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Riparian trees are particularly vulnerable to drought because they are highly dependent on water availability for their survival. However, the response of riparian tree species to water stress varies depending on regional hydroclimatic conditions, making them unevenly vulnerable to changing drought patterns. Understanding this spatial variability in stress responses requires a comprehensive assessment of water stress across broader spatial and temporal scales. Yet, the precise ecophysiological mechanisms underlying these responses remain poorly linked to remotely sensed indices. To address this gap, the implementation of remote sensing methods coupled with in situ validation is essential to obtain consistent results across diverse spatial and temporal contexts. We conducted a multi-tool analysis combining multispectral and thermal remote sensing indices with in situ ecophysiological measurements at different temporal scales to analyze the responses of white poplar (Populus alba) to seasonal changes in drought along a hydroclimatic gradient. Using this approach, we demonstrate that white poplars along the Rhône River (France) exhibit contrasting responses and behaviors during drought depending on the latitudinal context. White poplars in a Mediterranean climate show rapid stomatal closure to reduce water loss and maintain high minimum water potential levels, although this results in a decrease in remotely sensed greenness. Conversely, white poplars located upstream in a temperate climate show high transpiration and stable greenness but lower minimum water potential and water content. A site in the middle of the gradient has intermediate responses. These results demonstrate that white poplars along a climate gradient can have a range of responses to drought along the iso/anisohydricity continuum. These results are important for future climatic conditions because they show that the same species can have different mechanisms of drought resilience, even in the same river valley. This raises questions regarding how these riparian tree populations will respond to future climatic and hydrological conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Calliptamus italicus L. is a major pest in Xinjiang grassland. The diapause overwintering strategy is one of the important reasons for the large population of this pest. This study investigated the function of the genes associated with the release of diapause (DIB, JHE and CAM) in Calliptamus italicus by RNA interference (RNAi) technology to aid in its biological control., Results: The expression levels of DIB and its downstream-associated genes (EcR and FTZ-F1) in the eggs injected with dsDIB for 12 h decreased by 96.6%, 55.8% and 81.8%, respectively. Diapause began to terminate on day 3, and development was almost complete on day 6. However, the head was significantly smaller. The expression levels of JHE and its downstream-associated genes (JHEH and VgR) at 48 h after dsJHE treatment decreased by 76.5%, 85.6% and 85.9%, respectively. The termination of diapause occured on day 3 of incubation. The development was basically complete on day 6, but the yolk had been incompletely absorbed. The expression of CAM and its downstream-associated genes (CAMK4 and MYL) at 24 h after dsCAM treatment decreased by 42.4%, 95.3% and 82.7%, respectively. Diapause termination was completed on day 4 for incubation, and development was abnormal on day 6. The absorption of yolk was incomplete., Conclusion: DIB, JHE and CAM can delay the diapause termination of Calliptamus italicus eggs to different degrees and can be developed as potential target genes for its biological control. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Finding interventions to break the trade-off between reproduction and lifespan can provide insight into physiological limitations of animals. Effects of dietary protein quality on the trade-off are currently unclear, but clarity could lead to better designed diets that match animal needs. Dietary amino acid blends matching yolk proteins support reproduction and extend lifespan in fruit flies. To test if this is conserved across species, we matched dietary amino acids to vitellogenin to test reproduction and lifespan in adult females of the lubber grasshopper. Specifically, we compared varying degrees of protein quality by manipulating dietary essential amino acids. We identified a high-quality protein diet (amino acids matched to vitellogenin, or reproductive needs) that increased reproduction and matched lifespan in comparison to diets that differed only in the ratios of essential amino acids (i.e., were isocaloric and isonitrogenous). All these diets had longer lifespan but lower reproductive output than fully fed controls. In a separate experiment, full reproduction was possible on the high-quality artificial diet when offered at a 78% higher protein quantity and with a larger lettuce supplement (~ 17% of ad libitum). Additionally, we observed that as dietary protein quality was decreased (i.e., diets were less matched to vitellogenin), reproduction was reduced, and lifespan was extended in the more extreme scenarios. Taken together, these results indicate that the balance of dietary essential amino acids plays an important role in the lifespan and reproduction trade-off, while more work needs to be conducted to find the optimal diet mix for this species., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

The outbreak of the desert locust Schistocerca gregaria Forskål, 1775, which originated from the Horn of Africa in 2019-2020 created an episodic plague under bio-geographical settings in the arid and semi-arid areas of South and Southwest Asia. In India, it happened after twenty-seven years due to the persistence of a few favourable conditions caused by its plague, resulting in hundreds of crores in crop damage. Keeping this in mind, the study aims to assess the suitability and likelihood of the desert locust epidemic occurring in India, utilizing two widely recognized statistical models: Weight-of-Evidence (WoE) and Frequency Ratio (FR). This work evaluated nine critical climatic factors for the study considering western and central parts of India. The 'Projected Locust Suitability' (PLS) was calculated by analyzing the correlation of the considered variables and the occurrence of locust swarms and bands. The significance (importance) of each variable on PLS was determined using Principal Component Analysis (PCA) and Random Forest (RF) algorithms. The PLS maps clearly show that 42.7-52.8% of the areas fall under high and very high locust suitability zones. The result suggests that the Ajmer-Gwalior-Allahabad tract is highly prone to future locust occurrences, while the Aligarh-Bareilly-Lakhimpur tract is moderately susceptible. The effectiveness of both modelled PLS maps was determined with the help of the ROC curve. The AUC results indicate that both the WoE (0.92) and the RF (0.90) models worked remarkably well in precisely predicting PLS. The RF-based IncNodePurity analysis indicates that low to moderate temperatures in the presence of cloud cover significantly impact locust occurrence and migration. The present findings are projected to direct the development of sustainable locust management strategies utilizing proper land use policies in the tropical climate., (© 2024. The Author(s).)

Large mammalian herbivores (LMH) are important functional components and drivers of biodiversity and ecosystem functioning in grasslands. Yet their role in regulating food-web dynamics and trophic cascades remains poorly understood. In the temperate grasslands of northern China, we explored whether and how grazing domestic cattle ( Bos taurus ) alter the predator-prey interactions between a dominant grasshopper ( Euchorthippus unicolor ) and its avian predator the barn swallow ( Hirundo rustica ). Using two large manipulative field experiments, we found that in the presence of cattle, grasshoppers increased their jumping frequency threefold, swallows increased foraging visits to these fields sixfold, and grasshopper density was reduced by about 50%. By manipulatively controlling the grasshoppers' ability to jump, we showed that jumping enables grasshoppers to avoid being incidentally consumed or trampled by cattle. However, jumping behaviour increased their consumption rates by swallows 37-fold compared with grasshoppers that were unable to jump. Our findings illustrate how LMH can indirectly alter predator-prey interactions by affecting behaviour of avian predators and herbivorous insects. These non-plant-mediated effects of LMH may influence trophic interactions in other grazing ecosystems and shape community structure and dynamics. We highlight that convoluted multispecies interactions may better explain how LMH control food-web dynamics in grasslands.

Foraging for food is a rich and ubiquitous animal behavior that involves complex cognitive decisions, and interactions between different individuals and species. There has been exciting recent progress in understanding multi-agent foraging behavior from cognitive, neuroscience, and statistical perspectives, but integrating these perspectives can be elusive. This paper seeks to unify these perspectives, allowing statistical analysis of observational animal movement data to shed light on the viability of cognitive models of foraging strategies. We start with cognitive agents with internal preferences expressed as value functions, and implement this in a biologically plausible neural network, and an equivalent statistical model, where statistical predictors of agents' movements correspond to the components of the value functions. We test this framework by simulating foraging agents and using Bayesian statistical modeling to correctly identify the factors that best predict the agents' behavior. As further validation, we use this framework to analyze an open-source locust foraging dataset. Finally, we collect new multi-agent real-world bird foraging data, and apply this method to analyze the preferences of different species. Together, this work provides an initial roadmap to integrate cognitive, neuroscience, and statistical approaches for reasoning about animal foraging in complex multi-agent environments., (© 2024. The Author(s).)

Ceracris kiangsu (Orthoptera: Arcypteridae), is greatly affected by climatic factors and exhibits strong adaptability, posing a serious threat to the ecological environment. Therefore, predicting its potential suitable habitat distribution provides a proactive theoretical basis for pest control. This study using the Biomod2 package of R simulated and predicted the current and future potential distribution, area changes, changes in the center points of suitable habitats, and niche shifts of C. kiangsu under two different greenhouse gas emission scenarios, SSP1-26 and SSP5-85. The results show that: (1) Currently, the high suitability areas for C. kiangsu are mainly distributed in Yunnan, Jiangxi, Hunan provinces in southern China and phongsaly province in northern Laos. In the future, the center of the suitable habitat distribution pattern of C. kiangsu will remain unchanged, primarily expanding outward from medium and high suitability areas. Additionally, significant suitable habitats for C. kiangsu were discovered in Southeast Asian countries without previous pest records. (2) Compared to the present, the overall suitable habitat area for C. kiangsu is expected to expand, particularly under the SSP5-85 climate change scenario. (3) In the SSP1-26 and SSP5-85 climate scenarios, the geometric center of the suitable habitat generally shows a trend of gradually shifting northeast. (4) Under different climate scenarios, the suitable habitat of C. kiangsu has highly overlapping, indicating that the suitable habitat of C. kiangsu in the invaded areas is broader than in its native regions. In conclusion, the research findings represent a breakthrough in identifying the potential distribution areas of C. kiangsu, which is of great practical significance for the monitoring and control of C. kiangsu pest infestation in China and Southeast Asian countries., (© 2024. The Author(s).)

The female locust lays its eggs deep within soft substrate to protect them from predators and provide optimal conditions for successful development and hatching. During oviposition digging, the female's abdomen is pooled and extends into the ground, guided by a dedicated excavation mechanism at its tip, comprising two pairs of specialized digging valves. Little is known about how these active valves negotiate the various obstacles encountered on their path. In this study, female locusts oviposited their eggs in specialized sand-filled tubes with pre-inserted 3D-printed plastic obstacles. The subterranean route taken by the abdomen and digging valves upon encountering the obstacles was investigated, characterized, and compared to that in control tubes without obstacles. Data were obtained by way of visual inspection, by utilizing cone beam computed tomography scans in high-definition mode, and by making paraffin casts of the oviposition burrows (after egg hatching). We demonstrate, for the first time, the subterranean navigation ability of the female locust's excavation mechanism and its ability to circumvent obstacles during oviposition. Finally, we discuss the role of active sensory-motor mechanisms versus the passive embodied function of the valves, central control, and decision-making., (© 2024. The Author(s).)

Membrane technology advancements within the past twenty years have provided a new perspective on environmentalism as engineers design membranes to separate greenhouse gases from the environment. Several scientific journals have published articles of experimental evidence quantifying carbon dioxide (CO 2 ), a common greenhouse gas, separation using membrane technology and ranking them against one another. On the other hand, natural systems such as the respiratory system of mammals also accomplish transmembrane transport of CO 2 . However, to our knowledge, a comparison of these natural organic systems with engineered membranes has not yet been accomplished. The tracheal respiratory systems of insects transport CO 2 at the highest rates in the animal kingdom. Therefore, this work compares engineered membranes to the tracheal systems of insects by quantitatively comparing greenhouse gas conductance rates. We demonstrate that on a per unit volume basis, locusts can transport CO 2 approximately ∼100 times more effectively than the best current engineered systems. Given the same temperature conditions, insect tracheal systems transport CO 2 three orders of magnitude faster on average. Miniaturization of CO 2 capture systems based on insect tracheal system design has great potential for reducing cost and improving the capacities of industrial CO 2 capture., (© 2024 IOP Publishing Ltd.)

Behavioral responses to many odorants are not fixed but are flexible, varying based on organismal needs. How such variations arise and the role of various neuromodulators in achieving flexible neural-to-behavioral mapping is not fully understood. In this study, we examined how serotonin modulates the neural and behavioral responses to odorants in locusts ( Schistocerca americana ). Our results indicated that serotonin can increase or decrease appetitive behavior in an odor-specific manner. On the other hand, in the antennal lobe, serotonergic modulation enhanced odor-evoked response strength but left the temporal features or the combinatorial response profiles unperturbed. This result suggests that serotonin allows for sensitive and robust recognition of odorants. Nevertheless, the uniform neural response amplification appeared to be at odds with the observed stimulus-specific behavioral modulation. We show that a simple linear model with neural ensembles segregated based on behavioral relevance is sufficient to explain the serotonin-mediated flexible mapping between neural and behavioral responses., Competing Interests: YB, BR No competing interests declared, (© 2023, Bessonova and Raman.)

The representation of odors in the locust antennal lobe with its >2,000 glomeruli has long remained a perplexing puzzle. We employed the CRISPR-Cas9 system to generate transgenic locusts expressing the genetically encoded calcium indicator GCaMP in olfactory sensory neurons. Using two-photon functional imaging, we mapped the spatial activation patterns representing a wide range of ecologically relevant odors across all six developmental stages. Our findings reveal a functionally ring-shaped organization of the antennal lobe composed of specific glomerular clusters. This configuration establishes an odor-specific chemotopic representation by encoding different chemical classes and ecologically distinct odors in the form of glomerular rings. The ring-shaped glomerular arrangement, which we confirm by selective targeting of OR70a-expressing sensory neurons, occurs throughout development, and the odor-coding pattern within the glomerular population is consistent across developmental stages. Mechanistically, this unconventional spatial olfactory code reflects the locust-specific and multiplexed glomerular innervation pattern of the antennal lobe., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Accurate detection of pheromones is crucial for chemical communication and reproduction in insects. In holometabolous flies and moths, the sensory neuron membrane protein 1 (SNMP1) is essential for detecting long-chain aliphatic pheromones by olfactory neurons. However, its function in hemimetabolous insects and its role for detecting pheromones of a different chemical nature remain elusive. Therefore, we investigated the relevance of SNMP1 for pheromone detection in a hemimetabolous insect pest of considerable economic importance, the desert locust Schistocerca gregaria, which moreover employs the aromatic pheromone phenylacetonitrile (PAN) to govern reproductive behaviors., Results: Employing CRISPR/Cas-mediated gene editing, a mutant locust line lacking functional SNMP1 was established. In electroantennography experiments and single sensillum recordings, we found significantly decreased electrical responses to PAN in SNMP1-deficient (SNMP1 -/- ) locusts. Moreover, calcium imaging in the antennal lobe of the brain revealed a substantially reduced activation of projection neurons in SNMP1 -/- individuals upon exposure to PAN, indicating that the diminished antennal responsiveness to PAN in mutants affects pheromone-evoked neuronal activity in the brain. Furthermore, in behavioral experiments, PAN-induced effects on pairing and mate choice were altered in SNMP1 -/- locusts., Conclusions: Our findings emphasize the importance of SNMP1 for chemical communication in a hemimetabolous insect pest. Moreover, they show that SNMP1 plays a crucial role in pheromone detection that goes beyond long-chain aliphatic substances and includes aromatic compounds controlling reproductive behaviors., (© 2024. The Author(s).)

Platyrrhines consume many species of arthropods in the order Orthoptera. Some species of orthopterans can produce chemical defenses that render them toxic or unpalatable and thus act as predator deterrents. These species include the stick grasshoppers (family Proscopiidae), which are widely distributed in the Caatinga biome in northeastern Brazil, which comprises part of the distribution of capuchin monkeys. Capuchin monkeys are omnivores and consume a wide variety of foods, including unpleasant-tasting, potentially toxic items, which they need to learn how to process. We describe the processing of stick grasshoppers (Stiphra sp.) by wild capuchin monkeys (Sapajus libidinosus) that live in Serra da Capivara National Park, Brazil, and compare how individuals of different age classes handle these potentially toxic food items. S. libidinosus predominantly avoided consuming the digestive tract, which contains toxic compounds, when feeding on stick grasshoppers. Immatures took longer than adults to process the stick grasshoppers, indicating that capuchins need to learn how to process the toxic digestive tract of these prey to avoid consuming it., (© 2024. The Author(s).)

Thermochromic materials have been widely investigated due to their relevance in technological applications, including anti-counterfeiting materials, fashion accessories, displays, and temperature sensors. While many organisms exhibit color changes, few studies have explored the potential of the responsive natural materials for temperature sensing, especially given the often limited and irreversible nature of these changes in live specimens. Here, it is shown that the hindwings of the blue-winged grasshopper Coloracris azureus can act as a reversible, power-free bio-thermometer, transitioning from blue to purple/red in a 30-100°C temperature range. Using microspectrophotometry, light microscopy and Raman microscopy, it is found that the blue color of the wings originates from pigmentary coloration, based on a complex of astaxanthin and proteins. The thermochromic shift from blue to red, induced by a temperature increase, is attributed to a denaturation of this carotenoprotein complex, upon which astaxanthin is released. This process is reversible upon a subsequent temperature decrease. The color changes are both swift and consistent upon temperature change, making the grasshopper's wings suitable as direct visual sensors on thermally dynamic, curved surfaces. The potential possibilities of sustainable, power-free temperature sensors or microthermometers based on biomaterials are demonstrated., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Parasitism is known to affect the behavior of host species to enhance parasite dispersal and transmission. However, host behavioral responses to parasitism unrelated to parasite dispersal and transmission have been much less studied. The objective of this study was to determine whether grasshopper hosts infected and uninfected with a parasitic fly (Blaesoxipha sp.) differ in terms of the nutrient content of the diet they consume. We investigated the dietary preferences of two grasshopper species (i.e. Asulconotus chinghaiensis and Chorthippus fallax) in terms of the C/N composition of plant species consumed, and determined whether this affected the egg production of unparasitized and parasitized grasshoppers by flies in a Tibetan alpine meadow. The composition of plants consumed differed significantly between the unparasitized and parasitized grasshoppers. Specifically, the abundance of N-rich legumes was lower and that of high C/N grasses was higher in the diet of the parasitized compared to the unparasitized grasshoppers. Diet N content was higher and C/N was lower in the diet of unparasitized grasshoppers, and parasitized females produced fewer eggs than their unparasitized conspecifics. Future enquiries are needed to understand the specific mechanisms underlying these dietary differences. The effects of parasites on the fitness-associated behavior of hosts should be studied more broadly to better understand parasite evolution and adaptation., (© 2023 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.)

Desert locust plagues threaten the food security of millions. Central to their formation is crowding-induced plasticity, with social phenotypes changing from cryptic (solitarious) to swarming (gregarious). Here, we elucidate the implications of this transition on foraging decisions and corresponding neural circuits. We use behavioral experiments and Bayesian modeling to decompose the multi-modal facets of foraging, revealing olfactory social cues as critical. To this end, we investigate how corresponding odors are encoded in the locust olfactory system using in-vivo calcium imaging. We discover crowding-dependent synergistic interactions between food-related and social odors distributed across stable combinatorial response maps. The observed synergy was specific to the gregarious phase and manifested in distinct odor response motifs. Our results suggest a crowding-induced modulation of the locust olfactory system that enhances food detection in swarms. Overall, we demonstrate how linking sensory adaptations to behaviorally relevant tasks can improve our understanding of social modulation in non-model organisms., (© 2024. The Author(s).)

Grasshoppers represent a significant biological challenge in Inner Mongolia's grasslands, severely affecting the region's animal husbandry. Thus, dynamic monitoring of grasshopper infestation risk is crucial for sustainable livestock farming. This study employed the Maxent model, along with remote sensing data, to forecast Oedaleus decorus asiaticus occurrence during the growing season, using grasshopper suitability habitats as a base. The Maxent model's predictive accuracy was high, with an AUC of 0.966. The most influential environmental variables for grasshopper distribution were suitable habitat data (34.27%), the temperature-vegetation dryness index during the spawning period (18.81%), and various other meteorological and vegetation factors. The risk index model was applied to calculate the grasshopper distribution across different risk levels for the years 2019-2022. The data indicated that the level 1 risk area primarily spans central, eastern, and southwestern Inner Mongolia. By examining the variable weights, the primary drivers of risk level fluctuation from 2019 to 2022 were identified as accumulated precipitation and land surface temperature anomalies during the overwintering period. This study offers valuable insights for future O. decorus asiaticus monitoring in Inner Mongolia., (© The Author(s) 2024. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

RNA N 6 -methyladenosine (m 6 A), as the most abundant modification of messenger RNA, can modulate insect behaviors, but its specific roles in aggregation behaviors remain unexplored. Here, we conducted a comprehensive molecular and physiological characterization of the individual components of the methyltransferase and demethylase in the migratory locust Locusta migratoria. Our results demonstrated that METTL3, METTL14 and ALKBH5 were dominantly expressed in the brain and exhibited remarkable responses to crowding or isolation. The individual knockdown of methyltransferases (i.e., METTL3 and METTL14) promoted locust movement and conspecific attraction, whereas ALKBH5 knockdown induced a behavioral shift toward the solitary phase. Furthermore, global transcriptome profiles revealed that m 6 A modification could regulate the orchestration of gene expression to fine tune the behavioral aggregation of locusts. In summary, our in vivo characterization of the m 6 A functions in migratory locusts clearly demonstrated the crucial roles of the m 6 A pathway in effectively modulating aggregation behaviors., (© 2023. Science China Press.)

Detecting looming motion directly towards the insect is vital to its survival. Looming detection in two insects, flies and locusts, is described and contrasted. Pathways using looming detectors to trigger action and their topographical layout in the brain is explored in relation to facilitating behavioural selection. Similar visual stimuli, such as looming motion, are processed by nearby glomeruli in the brain. Insect-inspired looming motion detectors are combined to detect and avoid collision in different scenarios by robots, vehicles and unmanned aerial vehicle (UAV)s., Competing Interests: Declaration of Competing Interest None, (Copyright © 2024 The Author. Published by Elsevier Inc. All rights reserved.)

Background: The female locust is equipped with unique digging tools, namely two pairs of valves-a dorsal and a ventral-utilized for excavating an underground hole in which she lays her eggs. This apparatus ensures that the eggs are protected from potential predators and provides optimal conditions for successful hatching. The dorsal and the ventral valves are assigned distinct roles in the digging process. Specifically, the ventral valves primarily function as anchors during propagation, while the dorsal valves displace soil and shape the underground tunnel., Results: In this study, we investigated the noticeable asymmetry and distinct shapes of the valves, using a geometrical model and a finite element method. Our analysis revealed that although the two pairs of valves share morphological similarities, they exhibit different 3D characteristics in terms of absolute size and structure. We introduced a structural characteristic, the skew of the valve cross-section, to quantify the differences between the two pairs of valves. Our findings indicate that these structural variations do not significantly contribute to the valves' load-bearing capabilities under external forces., Conclusions: The evolutionary development of the form of the female locust digging valves is more aligned with fitting their respective functions rather than solely responding to biomechanical support needs. By understanding the intricate features of these locust valves, and using our geometrical model, valuable insights can be obtained for creating more efficient and specialized tools for various digging applications., (© 2024. The Author(s).)

To navigate their environment, insects need to keep track of their orientation. Previous work has shown that insects encode their head direction as a sinusoidal activity pattern around a ring of neurons arranged in an eight-column structure. However, it is unclear whether this sinusoidal encoding of head direction is just an evolutionary coincidence or if it offers a particular functional advantage. To address this question, we establish the basic mathematical requirements for direction encoding and show that it can be performed by many circuits, all with different activity patterns. Among these activity patterns, we prove that the sinusoidal one is the most noise-resilient, but only when coupled with a sinusoidal connectivity pattern between the encoding neurons. We compare this predicted optimal connectivity pattern with anatomical data from the head direction circuits of the locust and the fruit fly, finding that our theory agrees with experimental evidence. Furthermore, we demonstrate that our predicted circuit can emerge using Hebbian plasticity, implying that the neural connectivity does not need to be explicitly encoded in the genetic program of the insect but rather can emerge during development. Finally, we illustrate that in our theory, the consistent presence of the eight-column organisation of head direction circuits across multiple insect species is not a chance artefact but instead can be explained by basic evolutionary principles., Competing Interests: PV, DD, IP No competing interests declared, (© 2024, Vilimelis Aceituno, Dall'Osto et al.)

Bilateral symmetry is widespread across animals, yet, among bilaterians, many cases of conspicuous asymmetries evolved. This means that bilaterally homologous structures on the left and right sides display divergent phenotypes. The evolution of such divergent phenotypes between otherwise similarly shaped structures can be thought to be favored by modularity, but this has rarely been studied in the context of left-right differences. Here, we provide an empirical example, using geometric morphometrics to assess patterns of asymmetry and covariation between landmark partitions in a grasshopper with conspicuously asymmetric mandibles. Our morphometric data confirm the presence of strictly directional conspicuous asymmetry in the mandibles and surrounding structures. Covariance patterns and tests hint at a strong integration between mandibles despite their divergent morphologies, and variational modularity with the head capsule. While mandibles have been selected to achieve a key-and-lock morphology by having interlocking shapes, the developmental modularity required to achieve this seems to be overwritten by developmental and/or functional integration, allowing the precise matching required for feeding. The consequent conflicting covariation patterns are reminiscent of the palimpsest model. Finally, the degree of directional asymmetry appears to be under selection, although we find no relationship between bite force and mandible shape or asymmetry., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE).)

Sedentary animals choose appropriate refuges against predators, while migratory ones may not necessarily do so. In ectotherms, refuge selection is critical during low temperatures, because they cannot actively evade predators. To understand how migratory ectotherms alter their defensive behaviors depending on refuge quality in cold temperatures, we evaluated migratory gregarious desert locust nymphs (Schistocerca gregaria) in the Sahara Desert, where daily thermal constraints occur. We recorded how roosting plant type (bush/shrub) and its height influenced two alternative defense behaviors (dropping/stationary) during cold mornings, in response to an approaching simulated ground predator. Most locusts in bushes dropped within the bush and hid irrespective of their height, whereas those roosting > 2 m height in shrubs remained stationary. These defenses are effective and match with refuge plant types because dynamic locomotion is not required. When nymphs roosted on shrubs < 1.5-m height, which was an unsafe position, nearly half showed both defensive behaviors, indicating that escaping decisions become ambiguous when the refuges are inappropriate. These results suggest that locusts display flexible defensive behaviors when finding appropriate refuges and selecting refuge before daily thermal limitations occur could be critical for migratory ectotherms, which is a risk associated with migration., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Many theoretical treatments of foraging use energy as currency, with carbohydrates and lipids considered interchangeable as energy sources. However, herbivores must often synthesize lipids from carbohydrates since they are in short supply in plants, theoretically increasing the cost of growth. We tested whether a generalist insect herbivore ( Locusta migratoria ) can improve its growth efficiency by consuming lipids, and whether these locusts have a preferred caloric intake ratio of carbohydrate to lipid (C : L). Locusts fed pairs of isocaloric, isoprotein diets differing in C and L consistently selected a 2C : 1L target. Locusts reared on isocaloric, isoprotein 3C : 0L diets attained similar final body masses and lipid contents to locusts fed the 2C : 1L diet, but they ate more and had a ~12% higher metabolic rate, indicating an energetic cost for lipogenesis. These results demonstrate that some animals can selectively regulate carbohydrate-to-lipid intake and that consumption of dietary lipids can improve growth efficiency.

Intermittent motion is prevalent in animal locomotion. Of special interest is the case of collective motion, in which social and environmental information must be processed in order to establish coordinated movement. We explored this nexus in locust, focusing on how intermittent motion interacts with swarming-related visual-based decision-making. Using a novel approach, we compared individual locust behaviour in response to continuously moving stimuli, with their response in semi-closed-loop conditions, in which the stimuli moved either in phase with the locust walking, or out of phase, i.e. only during the locust's pauses. Our findings clearly indicate the greater tendency of a locust to respond and 'join the swarming motion' when the visual stimuli were presented during its pauses. Hence, the current study strongly confirms previous indications of the dominant role of pauses in the collective motion-related decision-making of locusts. The presented insights contribute to a deeper general understanding of how intermittent motion contributes to group cohesion and coordination in animal swarms.

The response of insects to climate changes in various aspects has been well-documented. However, there is a dearth of comprehensive review specifically focusing on the response and adaptation of grasshoppers, which are important primary consumers and pests in grassland and agricultural ecosystems. The coexistence of grasshopper species forms diverse communities and coherent groups in spatial-temporal scales. It makes them excellent models for studying the interplay of phenology, dispersal, trophic relationship, and population dynamics, all influenced by climate changes. Certain grasshopper species have adapted to climate change through mechanisms such as diapause. Here, we delve into grasshopper community changes, their adaptive strategies, and population outbreaks in response to climate change and land use. By serving as ecological indicators, grasshoppers offer valuable insights for monitoring climatic and environmental shifts. Last, this review puts forth several future directions for comprehending the population dynamics of insects in the context of climate change., Competing Interests: Declaration of Competing Interest The authors declare that there is no conflict of interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Alarm calls produced by basal prey have a well-known informative value. In multi-predator communities, mesopredators, when faced with top predators, may emit alarm calls that could inform basal prey about their lowered predation risk. To test this unexplored possibility, we conducted one field and one mesocosm experiment in which we simulated alarm and non-alarm calls from little owls ( Athene noctua ) as mesopredators and measured their effects on grasshoppers as prey of little owls but not of top predators. In the field experiment, we found that grasshopper species were significantly more abundant in patches where we simulated either the presence of scared little owls (alarm treatment) or no owls (control treatment) compared to patches where the presence of non-scared little owls (non-alarm treatment) was simulated. In the mesocosm experiment, locusts ( Locusta migratoria ) moved significantly more to exposed areas when we simulated the presence of scared little owls (alarm treatment) or of a granivorous bird (control treatment), while they moved to sheltered areas when we simulated the presence of non-scared owls (non-alarm treatment). These results show that prey could cue on predators' calls to assess their predation risk and make decisions, revealing unprecedented potential ecological consequences of alarm calls in invertebrate communities.

Insect cuticle is an evolutionary-malleable exoskeleton that has specialised for various functions. Insects that detect the pressure component of sound bear specialised sound-capturing tympani evolved from cuticular thinning. Whilst the outer layer of insect cuticle is composed of non-living chitin, its mechanical properties change during development and aging. Here, we measured the displacements of the tympanum of the desert Locust, Schistocerca gregaria, to understand biomechanical changes as a function of age and noise-exposure. We found that the stiffness of the tympanum decreases within 12 h of noise-exposure and increases as a function of age, independent of noise-exposure. Noise-induced changes were dynamic with an increased tympanum displacement to sound within 12 h post noise-exposure. Within 24 h, however, the tone-evoked displacement of the tympanum decreased below that of control Locusts. After 48 h, the tone-evoked displacement of the tympanum was not significantly different to Locusts not exposed to noise. Tympanal displacements reduced predictably with age and repeatably noise-exposed Locusts (every three days) did not differ from their non-noise-exposed counterparts. Changes in the biomechanics of the tympanum may explain an age-dependent decrease in auditory detection in tympanal insects., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2023. Published by Elsevier Ltd. All rights reserved.)

The Orthoptera are a diverse insect order well known for their locomotive capabilities. To jump, the bush-cricket uses a muscle actuated (MA) system in which leg extension is actuated by contraction of the femoral muscles of the hind legs. In comparison, the locust uses a latch mediated spring actuated (LaMSA) system, in which leg extension is actuated by the recoil of spring-like structure in the femur. The aim of this study was to describe the jumping kinematics of Mecopoda elongata (Tettigoniidae) and compare this to existing data in Schistocerca gregaria (Acrididae), to determine differences in control of rotation during take-off between similarly sized MA and LaMSA jumpers. 269 jumps from 67 individuals of M. elongata with masses from 0.014 g to 3.01 g were recorded with a high-speed camera setup. In M. elongata, linear velocity increased with mass 0.18 and the angular velocity (pitch) decreased with mass -0.13 . In S. gregaria, linear velocity is constant and angular velocity decreases with mass -0.24 . Despite these differences in velocity scaling, the ratio of translational kinetic energy to rotational kinetic energy was similar for both species. On average, the energy distribution of M. elongata was distributed 98.8% to translational kinetic energy and 1.2% to rotational kinetic energy, whilst in S. gregaria it is 98.7% and 1.3%, respectively. This energy distribution was independent of size for both species. Despite having two different jump actuation mechanisms, the ratio of translational and rotational kinetic energy formed during take-off is fixed across these distantly related orthopterans., (© 2023. The Author(s).)

Collision detection is critical for autonomous vehicles or robots to serve human society safely. Detecting looming objects robustly and timely plays an important role in collision avoidance systems. The locust lobula giant movement detector (LGMD1) is specifically selective to looming objects which are on a direct collision course. However, the existing LGMD1 models cannot distinguish a looming object from a near and fast translatory moving object, because the latter can evoke a large amount of excitation that can lead to false LGMD1 spikes. This article presents a new visual neural system model (LGMD1) that applies a neural competition mechanism within a framework of separated ON and OFF pathways to shut off the translating response. The competition-based approach responds vigorously to monotonous ON/OFF responses resulting from a looming object. However, it does not respond to paired ON-OFF responses that result from a translating object, thereby enhancing collision selectivity. Moreover, a complementary denoising mechanism ensures reliable collision detection. To verify the effectiveness of the model, we have conducted systematic comparative experiments on synthetic and real datasets. The results show that our method exhibits more accurate discrimination between looming and translational events-the looming motion can be correctly detected. It also demonstrates that the proposed model is more robust than comparative models.

Owing to alignment of rhodopsin in microvillar photoreceptors, insects are sensitive to the oscillation plane of polarized light. This property is used by many species to navigate with respect to the polarization pattern of light from the blue sky. In addition, the polarization angle of light reflected from shiny surfaces such as bodies of water, animal skin, leaves, or other objects can enhance contrast and visibility. Whereas photoreceptors and central mechanisms involved in celestial polarization vision have been investigated in great detail, little is known about peripheral and central mechanisms of sensing the polarization angle of light reflected from objects and surfaces. Desert locusts, like other insects, use a polarization-dependent sky compass for navigation but are also sensitive to polarization angles from horizontal directions. In order to further analyze the processing of polarized light reflected from objects or water surfaces, we tested the sensitivity of brain interneurons to the angle of polarized blue light presented from ventral direction in locusts that had their dorsal eye regions painted black. Neurons encountered interconnect the optic lobes, invade the central body, or send descending axons to the ventral nerve cord but are not part of the polarization vision pathway involved in sky-compass coding., (© 2023. The Author(s).)

In most animals, multiple external and internal signals are integrated by the brain, transformed and, finally, transmitted as commands to motor centers. In insects, the central complex is a motor control center in the brain, involved in decision-making and goal-directed navigation. In desert locusts, it encodes celestial cues in a compass-like fashion indicating a role in sky-compass navigation. While several descending brain neurons (DBNs) including two neurons transmitting sky compass signals have been identified in the locust, a complete analysis of DBNs and their relationship to the central complex is still lacking. As a basis for further studies, we used Neurobiotin tracer injections into a neck connective to map the organization of DBNs in the brain. Cell counts revealed a maximum of 324 bilateral pairs of DBNs with somata distributed in 14 ipsilateral and nine contralateral groups. These neurons invaded most brain neuropils, especially the posterior slope, posterior and ventro-lateral protocerebrum, the antennal mechanosensory and motor center, but less densely the lateral accessory lobes that are targeted by central-complex outputs. No arborizations were found in the central complex and only few processes in the mushroom body, antennal lobe, lobula, medulla, and superior protocerebrum. Double label experiments provide evidence for the presence of GABA, dopamine, tyramine, but not serotonin, in small sets of DBNs. The data show that some DBNs may be targeted directly by central-complex outputs, but many others are likely only indirectly influenced by central-complex networks, in addition to input from multiple other brain areas., (© 2023 The Authors. The Journal of Comparative Neurology published by Wiley Periodicals LLC.)

In animal species ranging from invertebrate to mammals, visually guided escape behaviours have been studied using looming stimuli, the two-dimensional expanding projection on a screen of an object approaching on a collision course at constant speed. The peak firing rate or membrane potential of neurons responding to looming stimuli often tracks a fixed threshold angular size of the approaching stimulus that contributes to the triggering of escape behaviours. To study whether this result holds more generally, we designed stimuli that simulate acceleration or deceleration over the course of object approach on a collision course. Under these conditions, we found that the angular threshold conveyed by collision detecting neurons in grasshoppers was sensitive to acceleration whereas the triggering of escape behaviours was less so. In contrast, neurons in goldfish identified through the characteristic features of the escape behaviours they trigger, showed little sensitivity to acceleration. This closely mirrored a broader lack of sensitivity to acceleration of the goldfish escape behaviour. Thus, although the sensory coding of simulated colliding stimuli with non-zero acceleration probably differs in grasshoppers and goldfish, the triggering of escape behaviours converges towards similar characteristics. Approaching stimuli with non-zero acceleration may help refine our understanding of neural computations underlying escape behaviours in a broad range of animal species. KEY POINTS: A companion manuscript showed that two mathematical models of collision-detecting neurons in grasshoppers and goldfish make distinct predictions for the timing of their responses to simulated objects approaching on a collision course with non-zero acceleration. Testing these experimental predictions showed that grasshopper neurons are sensitive to acceleration while goldfish neurons are not, in agreement with the distinct models proposed previously in these species using constant velocity approaches. Grasshopper and goldfish escape behaviours occurred after the stimulus reached a fixed angular size insensitive to acceleration, suggesting further downstream processing in grasshopper motor circuits to match what was observed in goldfish. Thus, in spite of different sensory processing in the two species, escape behaviours converge towards similar solutions. The use of object acceleration during approach on a collision course may help better understand the neural computations implemented for collision avoidance in a broad range of species., (© 2023 The Authors. The Journal of Physiology © 2023 The Physiological Society.)

Chemical signals from conspecifics are essential in insect group formation and maintenance. Migratory locusts use the aggregation pheromone 4-vinylanisole (4VA), specifically released by gregarious locusts, to attract and recruit conspecific individuals, leading to the formation of large-scale swarms. However, how 4VA contributes to the transition from solitary phase to gregarious phase remains unclear. We investigated the occurrence of locust behavioral phase changes in the presence and absence of 4VA perception. The findings indicated that solitary locusts require crowding for 48 and 72 h to adopt partial and analogous gregarious behavior. However, exposure to increased concentrations of 4VA enabled solitary locusts to display behavioral changes within 24 h of crowding. Crowded solitary locusts with RNAi knockdown of Or35 , the specific olfactory receptor for 4VA, failed to exhibit gregarious behaviors. Conversely, the knockdown of Or35 in gregarious locusts resulted in the appearance of solitary behavior. Additionally, a multi-individual behavioral assay system was developed to evaluate the interactions among locust individuals, and four behavioral parameters representing the inclination and conduct of social interactions were positively correlated with the process of crowding. Our data indicated that exposure to 4VA accelerated the behavioral transition from solitary phase to gregarious phase by enhancing the propensity toward proximity and body contact among conspecific individuals. These results highlight the crucial roles of 4VA in the behavioral phase transition of locusts. Furthermore, this study offers valuable insights into the mechanisms of behavioral plasticity that promote the formation of locust swarms and suggests the potential for 4VA application in locust control.

Many arthropods and vertebrates use celestial signals such as the position of the sun during the day or stars at night as compass cues for spatial orientation. The neural network underlying sky compass coding in the brain has been studied in great detail in the desert locust Schistocerca gregaria. These insects perform long-range migrations in Northern Africa and the Middle East following seasonal changes in rainfall. Highly specialized photoreceptors in a dorsal rim area of their compound eyes are sensitive to the polarization of the sky, generated by scattered sunlight. These signals are combined with direct information on the sun position in the optic lobe and anterior optic tubercle and converge from both eyes in a midline crossing brain structure, the central complex. Here, head direction coding is achieved by a compass-like arrangement of columns signaling solar azimuth through a 360° range of space by combining direct brightness cues from the sun with polarization cues matching the polarization pattern of the sky. Other directional cues derived from wind direction and internal self-rotation input are likely integrated. Signals are transmitted as coherent steering commands to descending neurons for directional control of locomotion and flight., (© 2022. The Author(s).)

An anticannibalistic signaling pathway offers a new understanding of locust swarm formation.

Flexible orientation through any environment requires a sense of current relative heading that is updated based on self-motion. Global external cues originating from the sky or the earth's magnetic field and local cues provide a reference frame for the sense of direction. Locally, optic flow may inform about turning maneuvers, travel speed and covered distance. The central complex in the insect brain is associated with orientation behavior and largely acts as a navigation center. Visual information from global celestial cues and local landmarks are integrated in the central complex to form an internal representation of current heading. However, it is less clear how optic flow is integrated into the central-complex network. We recorded intracellularly from neurons in the locust central complex while presenting lateral grating patterns that simulated translational and rotational motion to identify these sites of integration. Certain types of central-complex neurons were sensitive to optic-flow stimulation independent of the type and direction of simulated motion. Columnar neurons innervating the noduli, paired central-complex substructures, were tuned to the direction of simulated horizontal turns. Modeling the connectivity of these neurons with a system of proposed compass neurons can account for rotation-direction specific shifts in the activity profile in the central complex corresponding to turn direction. Our model is similar but not identical to the mechanisms proposed for angular velocity integration in the navigation compass of the fly Drosophila ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Zittrell, Pabst, Carlomagno, Rosner, Pegel, Endres and Homberg.)

The processing of visual information for collision avoidance has been investigated at the biophysical level in several model systems. In grasshoppers, the (so-called) [Formula: see text] model captures reasonably well the visual processing performed by an identified neuron called the lobular giant movement detector as it tracks approaching objects. Similar phenomenological models have been used to describe either the firing rate or the membrane potential of neurons responsible for visually guided collision avoidance in other animals. Specifically, in goldfish, the [Formula: see text] model has been proposed to describe the Mauthner cell, an identified neuron involved in startle escape responses. In the vinegar fly, a third model was developed for the giant fiber neuron, which triggers last resort escapes immediately before an impending collision. One key property of these models is their prediction that peak neuronal responses occur at a fixed delay after the simulated approaching object reaches a threshold angular size on the retina. This prediction is valid for simulated objects approaching at a constant speed. We tested whether it remains valid when approaching objects accelerate. After characterizing and comparing the models' responses to accelerating and constant speed stimuli, we find that the prediction holds true for the [Formula: see text] and the giant fiber model, but not for the [Formula: see text] model. These results suggest that acceleration in the approach trajectory of an object may help distinguish and further constrain the neuronal computations required for collision avoidance in grasshoppers, fish and vinegar flies., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Phenotypic plasticity in body size is a product of modification of the developmental pathway. Although hatchlings of the desert locust, Schistocerca gregaria, show egg size-dependent plasticity in body size, it remains unclear how embryogenesis during egg development regulates final embryonic body size. To determine the developmental pathway causing body size variation at hatching, we examined egg and embryonic development at the early, middle, and late egg developmental stages in S. gregaria by comparing small and large eggs. Crowd-reared females produced larger eggs than isolated-reared females. The daily egg developmental rate was similar between small and large eggs: eggs dramatically absorbed external water after days 3 to 7 and nearly doubled the initial egg weight at the late stage of day 12. Morphological measurements of eggs and embryos at different days after oviposition revealed that large eggs were longer than small eggs throughout developmental stages. However, embryo length was similar between small and large eggs at the early stage (anatrepsis). Embryos begin to absorb yolk into their bodies after blastokinesis. The size of large-egg embryos increased significantly from the middle stage (katatrepsis) due to absorption of more yolk than small eggs. Egg length and embryo length were conspicuously larger in large eggs than in small eggs on day 12 of late katatrepsis. These results suggest that egg size did not influence the egg developmental rate and initial embryo size. Large eggs had more yolk and space, resulting in larger final embryos than small eggs. The amount of yolk and size of eggshells during katatrepsis could play a key role in determining hatchling body size in S. gregaria., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Locusts (Schistocerca gregaria) jump using a latch mediated spring actuated system in the femur-tibia joint of their metathoracic legs. These jumps are exceptionally fast and display angular rotation immediately after take-off. In this study, we focus on the angular velocity, at take-off, of locusts ranging between 0.049 and 1.50 g to determine if and how rotation-rate scales with size. From 263 jumps recorded from 44 individuals, we found that angular velocity scales with mass -0.33 , consistent with a hypothesis of locusts having a constant rotational kinetic energy density. Within the data from each locust, angular velocity increased proportionally with linear velocity, suggesting the two cannot be independently controlled and thus a fixed energy budget is formed at take-off. On average, the energy budget of a jump is distributed 98.7% to translational kinetic energy and gravitational potential energy, and 1.3% to rotational kinetic energy. The percentage of energy devoted to rotation was constant across all sizes of locusts and represents a very small proportion of the energy budget. This analysis suggests that smaller locusts find it harder to jump without body rotation., (© 2023. The Author(s).)

Most terrestrial animals are constrained by extreme heat conditions such as midday desert environments, while a few terrestrial ectothermic insects are active in such ecological niches. Sexually mature males of the desert locust (Schistocerca gregaria) in the Sahara Desert remain on the open ground, despite the ground temperatures exceeding their lethal limit, to form leks and to mate incoming gravid females during the daytime. Lekking male locusts apparently suffer from extreme heat stress and greatly fluctuating thermal conditions. The present study examined the thermoregulatory strategies of the lekking male S. gregaria. Our field observations showed that lekking males changed their body orientation toward the sun depending on the temperature and time of day. In the relatively cool morning, males basked by orienting perpendicular to the sun's rays, maximizing the area of body surface exposed to the sun's rays. In contrast, around midday, when the ground surface temperature exceeded lethal high temperatures, some males tended to shelter inside the plants or remain in the shade. However, the remainder stayed on the ground, stilted (i.e., extending their legs to raise their bodies off the hot ground) and oriented parallel to the sun's rays, which minimized radiative heating. Measurements of body temperature throughout the hot middle period of the day confirmed that the stilting posture prevented overheating. Their critical lethal body temperature was as high as 54.7 °C. In this lekking system, gravid females enter male leks by flying. These incoming females usually landed on open ground, whereupon nearby males immediately approached, mounted, and mated the female, implying that males with greater heat-tolerance can increase mating chance. These results suggest that behavioral thermoregulation and physiologically high heat tolerance of male desert locusts allows them to endure extreme thermal conditions for lekking., Competing Interests: Declaration of competing interest None., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Migration allows animals to track favorable environments and avoid harmful conditions. However, migration is energetically costly, so migrating animals must prepare themselves by increasing their energy stores. Despite the importance of locust migratory swarms, we still understand little about the physiology of locust migration. During long-distance flight, locusts rely on lipid oxidation, despite the fact that lipids are relatively rare in their leaf-based diets. Therefore, locusts and other insect herbivores synthesize and store lipid from ingested carbohydrates, which are also important for initial flight. These data suggest that diets high in carbohydrate should increase lipid stores and the capacity for migratory flight in locusts. As predicted, locust lipid stores and flight performance increased with an increase in the relative carbohydrate content in their food. However, locust flight termination was not associated with complete lipid depletion. We propose potential testable mechanisms that might explain how macronutrient consumption can affect flight endurance., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

The phase transition from solitary to gregarious locusts is crucial in outbreaks of locust plague, which threaten agricultural yield and food security. Research on the regulatory mechanisms of phase transition in locusts has focused primarily on the transcriptional or posttranslational level. However, the translational regulation of phase transition is unexplored. Here, we show a phase-dependent pattern at the translation level, which exhibits different polysome profiles between gregarious and solitary locusts. The gregarious locusts exhibit significant increases in 60S and polyribosomes, while solitary locusts possess higher peaks of the monoribosome and a specific "halfmer." The polysome profiles, a molecular phenotype, respond to changes in population density. In gregarious locusts, ten genes involved in the cytosolic ribosome pathway exhibited increased translational efficiency (TE). In solitary locusts, five genes from the mitochondrial ribosome pathway displayed increased TE. The high expression of large ribosomal protein 7 at the translational level promotes accumulation of the free 60S ribosomal subunit in gregarious locusts, while solitary locusts employ mitochondrial small ribosomal protein 18c to induce the assembly of mitochondrial ribosomes, causing divergence of the translational profiles and behavioral transition. This study reveals the translational regulatory mechanism of locust phase transition, in which the locusts employ divergent ribosome pathways to cope with changes in population density.

Collectively moving groups of animals rely on the decision-making of locally interacting individuals in order to maintain swarm cohesion. However, the complex and noisy visual environment poses a major challenge to the extraction and processing of relevant information. We addressed this challenge by studying swarming-related decision-making in desert locust last-instar nymphs. Controlled visual stimuli, in the form of random dot kinematograms, were presented to tethered locust nymphs in a trackball set-up, while monitoring movement trajectory and walking parameters. In a complementary set of experiments, the neurophysiological basis of the observed behavioural responses was explored. Our results suggest that locusts use filtering and discrimination upon encountering multiple stimuli simultaneously. Specifically, we show that locusts are sensitive to differences in speed at the individual conspecific level, and to movement coherence at the group level, and may use these to filter out non-relevant stimuli. The locusts also discriminate and assign different weights to different stimuli, with an observed interactive effect of stimulus size, relative abundance and motion direction. Our findings provide insights into the cognitive abilities of locusts in the domain of decision-making and visual-based collective motion, and support locusts as a model for investigating sensory-motor integration and motion-related decision-making in the intricate swarm environment.

The aggregation of locusts from solitary to gregarious phases is crucial for the formation of devastating locust plagues. Locust management requires research on the prevention of aggregation or alternative and greener solutions to replace insecticide use, and insect-derived microRNAs (miRNAs) show the potential for application in pest control. Here, we performed a genome-wide screen of the differential expression of miRNAs between solitary and gregarious locusts and showed that miR-8-5p controls the γ-aminobutyric acid (GABA)/glutamate functional balance by directly targeting glutamate decarboxylase (Gad). Blocking glutamate-GABA neurotransmission by miR-8-5p overexpression or Gad RNAi in solitary locusts decreased GABA production, resulting in locust aggregation behavior. Conversely, activating this pathway by miR-8-5p knockdown in gregarious locusts induced GABA production to eliminate aggregation behavior. Further results demonstrated that ionotropic glutamate/GABA receptors tuned glutamate/GABA to trigger/hamper the aggregation behavior of locusts. Finally, we successfully established a transgenic rice line expressing the miR-8-5p inhibitor by short tandem target mimic (STTM). When locusts fed on transgenic rice plants, Gad transcript levels in the brain increased greatly, and aggregation behavior was lost. This study provided insights into different regulatory pathways in the phase change of locusts and a potential control approach through behavioral regulation in insect pests.

Neurons receive information through their synaptic inputs, but the functional significance of how those inputs are mapped on to a cell's dendrites remains unclear. We studied this question in a grasshopper visual neuron that tracks approaching objects and triggers escape behavior before an impending collision. In response to black approaching objects, the neuron receives OFF excitatory inputs that form a retinotopic map of the visual field onto compartmentalized, distal dendrites. Subsequent processing of these OFF inputs by active membrane conductances allows the neuron to discriminate the spatial coherence of such stimuli. In contrast, we show that ON excitatory synaptic inputs activated by white approaching objects map in a random manner onto a more proximal dendritic field of the same neuron. The lack of retinotopic synaptic arrangement results in the neuron's inability to discriminate the coherence of white approaching stimuli. Yet, the neuron retains the ability to discriminate stimulus coherence for checkered stimuli of mixed ON/OFF polarity. The coarser mapping and processing of ON stimuli thus has a minimal impact, while reducing the total energetic cost of the circuit. Further, we show that these differences in ON/OFF neuronal processing are behaviorally relevant, being tightly correlated with the animal's escape behavior to light and dark stimuli of variable coherence. Our results show that the synaptic mapping of excitatory inputs affects the fine stimulus discrimination ability of single neurons and document the resulting functional impact on behavior., Competing Interests: RD, YZ, ME, RM, FG No competing interests declared, (© 2022, Dewell, Zhu et al.)

The central complex in the brain of insects provides a neural network for sensorimotor processing that is essential for spatial navigation and locomotion and plays a role in sleep control. Studies on the neurochemical architecture of the central complex have been performed especially in the fruit fly Drosophila melangoaster and the desert locust, Schistocerca gregaria. In several insect species, myoinhibitory peptides (MIPs) are involved in circadian control and sleep-wake regulation. To identify neurons that might underlie these functions, we investigated the distribution of MIPs in the central complex of the locust. In silico transcript analysis suggests the presence of eight different MIPs in the desert locust. Through immunolabeling, we identified five systems of central-complex neurons that express MIP-like peptides. Two systems constitute columnar neurons of the protocerebral bridge and the lower division of the central body, while the other three systems are columnar neurons (two systems) and tangential neurons (one system) of the upper division of the central body. The innervation pattern and cell count of two systems of columnar neurons revealed the existence of 18 instead of 16 columns of the protocerebral bridge. Immunostaining of preparations containing intracellularly stained single cells allowed us to further specify subtypes of labeled columnar neurons. Double-label experiments showed that three systems of MIP-immunostained columnar neurons are also locustatachykinin-immunoreactive. No colocalization was found with serotonin immunostaining. The data provide novel insights into the architecture of the locust central complex and suggest that MIPs play a prominent role within the central-complex network., (© 2022 The Authors. The Journal of Comparative Neurology published by Wiley Periodicals LLC.)

Activity of an innervated tissue can be modulated based on an acquired biomarker through feedback loops. How to convert this biomarker into a meaningful stimulation pattern is still a topic of intensive research. In this article, we present a simple closed-loop mechanism to control the mean angle of a locust's leg in real time by modulating the frequency of the stimulation on its extensor motor nerve. The nerve is interfaced with a custom-designed cuff electrode and the feedback loop is implemented online with a proportional control algorithm, which runs solely on a microcontroller without the need of an external computer. The results show that the system can be controlled with a single-input, single-output feedback loop. The model described in this article can serve as a primer for young researchers to learn about neural control in biological systems before applying these concepts in advanced systems. We expect that the approach can be advanced to achieve control over more complex movements by increasing the number of recorded biomarkers and selective stimulation units., (© 2022. The Author(s).)