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Biological aggregations such as fish schools, bird flocks, bacterial colonies, and insect swarms have characteristic morphologies governed by the group members' intrinsic social interactions with each other and by their interactions with the external environment. Starting from a simple discrete model treating individual organisms as point particles, we derive a nonlocal partial differential equation describing the evolving population density of a continuum aggregation. To study equilibria and their stability, we use tools from the calculus of variations. In one spatial dimension, and for several choices of social forces, external forces, and domains, we find exact analytical expressions for the equilibria. These solutions agree closely with numerical simulations of the underlying discrete model. The analytical solutions provide a sampling of the wide variety of equilibrium configurations possible within our general swarm modeling framework, and include features such as spatial localization with compact support, mass concentrations, and discontinuous density jumps at the edge of the group. We apply our methods to a model of locust swarms, which in nature are observed to consist of a concentrated population on the ground separated from an airborne group. Our model can reproduce this configuration; in this case quasi-two-dimensionality of the locust swarm plays a critical role. [ABSTRACT FROM AUTHOR]

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Benefits and costs of parental care are expected to change with offspring development and lead to age-dependent coadaptation expressed as phenotypic (behavioural) matches between offspring age and parental reproductive stage. Parents and offspring interact repeatedly over time for the provision of parental care. Their behaviours should be accordingly adjusted to each other dynamically and adaptively, and the phenotypic match between offspring age and parental stage should stabilize the repeated behavioural interactions. In the European earwig ( Forficula auricularia), maternal care is beneficial for offspring survival, but not vital, allowing us to investigate the extent to which the stability of mother-offspring aggregation is shaped by age-dependent coadaptation. In this study, we experimentally cross-fostered nymphs of different age classes (younger or older) between females in early or late reproductive stage to disrupt age-dependent coadaptation, thereby generating female-nymph dyads that were phenotypically matched or mismatched. The results revealed a higher stability in aggregation during the first larval instar when care is most intense, a steeper decline in aggregation tendency over developmental time and a reduced developmental rate in matched compared with mismatched families. Furthermore, nymph survival was positively correlated with female-nymph aggregation stability during the early stages when maternal care is most prevalent. These results support the hypothesis that age-related phenotypically plastic coadaptation affects family dynamics and offspring developmental rate. [ABSTRACT FROM AUTHOR]

Warning signals are expected to evolve towards conspicuousness and monomorphism, and thereby hamper the evolution of multiple colour morphs. Here, we test fitness responses to different rearing densities to explain colour polymorphism in aposematic wood tiger moth ( Parasemia plantaginis) males., We used larval lines sired by white or yellow adult males selected for small or large melanization patterns of coloration. We reared these selected lines either solitarily (favourable conditions) or in aggregations (challenged conditions), and followed their performance to adult stage. We tested whether differences in larval density affected life-history traits, adult melanin expression, adult morph (white or yellow) survival and immunological responses., We found that the aggregated environment increased mortality of larvae, but decreased larval developmental time and pupa weight. Adult wing melanin pigmentation was dependent on larval melanin expression but not rearing density. We also confirmed that adult wing coloration had a genetic basis (h2 = 0·42) and was not influenced by larval growth density. Adult yellow males survived better from aggregations in comparison with white males, which may be related to differences in immune defence. White males had better encapsulation ability, whereas yellow males had increased lytic activity of haemolymph in the aggregations., Our main results highlight, that morph-linked immune responses mediated by differential growth density may facilitate the maintenance of colour polymorphism in aposematic species. In nature, risk of diseases and parasites vary spatially and temporally. Therefore, both yellow and white adult morphs can be maintained due to their differential investment in immune defence in heterogeneous environments. [ABSTRACT FROM AUTHOR]

Terrestrial isopods are known to be sensitive to humidity, brightness or temperature. Until now, aggregation was assumed to depend on these sensitivities as a result of individual preferences. In this paper, we show that the social component is also important in the isopod aggregation phenomenon. In experimental arenas with two identical shelters up to nearly 90% of woodlice aggregated under shelters. This aggregation was quick as in 10 minutes most of the animals aggregated, irrespective of their density. Nonetheless, 10-15% of the animals walked around the arena, rarely forming very small and short-lasting aggregates outside shelters. Woodlice aggregated preferably under one of the shelters in 77% of experiments. Indeed, almost 80% of the animals out of 40, 60 or 80 animals in the arena aggregated under one shelter. In arenas with 100 individuals the aggregations were proportionally smaller (70%). Our results revealed that 70 animals was a maximum number of woodlice in an aggregate. We concluded that the location of aggregates is strongly governed by individual preferences but the dynamics of aggregation and collective choice are controlled by social interaction between congeners. The tested densities of the animals in the arena did not impact the aggregation patterns. [ABSTRACT FROM AUTHOR]

. 1. The analysis of β-diversity, i.e. species turnover, across space is central to a wide array of ecological and evolutionary topics, also providing critical information to conservation planning. Although dispersal limitation has been demonstrated to play an important role in determining insect community structure, very little research has been done to test whether mobility might affect the diversity distribution of species across multiple spatial scales. 2. We considered orthopterans ( Ensifera and Caelifera) inhabiting hay meadows to test whether species mobility modifies β-diversity patterns across three nested spatial scales (1-m2 plots within meadow, 1000-m2 meadows within landscape, and 19.6-km2 landscapes within a region) and along a gradient of management intensity. 3. Orthopteran community composition varied most significantly over broader spatial scales. Larger proportion of regional γ-diversity was mainly composed of β-diversity at the landscape scale, whereas this proportion was smaller at the plot and meadow scale. 4. Mobility, but not management, strongly modified β-diversity patterns. Sedentary species contributed to a greater proportion of β-diversity across all the investigated scales compared with mobile species. 5. Measures currently included in most agri-environment schemes have only focused on the extensive management at the field scale. Our results imply that orthopteran diversity would benefit from maintaining extensively managed meadows scattered throughout the whole region, as the loss of species-rich isolated grassland patches due to abandonment or eutrophication might cause severe reductions of the regional species pool. Increasing connectivity might be also considered as a complementary measure to increase species occupancy and population persistence, particularly for sedentary species. [ABSTRACT FROM AUTHOR]

. 1. Agricultural intensification is a major cause of biodiversity loss in European farmlands. Grasslands are particularly important habitats for the conservation of rich insect assemblages of Central and Eastern Europe. Although regular grazing or mowing of these grasslands is required to maintain diversity, there is no information about how such management and other factors influence Hemiptera assemblages. 2. We studied leafhopper and true bug assemblages in semi-natural grasslands in three regions of the Great Hungarian Plain. We investigated how local vegetation factors and landscape complexity influence assemblages and whether they interact with management effects. 3. Seven pairs of intensively (>1 cow/ha) versus extensively (∼0.5 cow/ha) grazed pastures were sampled in each region by sweep-netting. 4. Sward height was the most important explanatory factor for leafhoppers (84 species, 27264 individuals), as it increased both species number and abundance, and influenced assemblage composition. The extent of grassland surrounding the sample sites negatively affected leafhoppers, whereas extensive grazing decreased abundance and influenced composition. True bug assemblages (140 species, 6656 individuals) were positively affected only by mean sward height, whereas regional differences determined the community composition of both taxa. 5. We conclude that vegetation structure is the primary factor shaping Hemiptera communities and that the various types of grasslands studied are all important habitats for the taxon. Therefore, cattle grazing in its current form is beneficial for the rich Hemiptera fauna in lowland pastures of Hungary. However, in some cases, local and landscape factors and great regional differences may confound the effects of grazing, and this must be considered in conservation planning in the future. [ABSTRACT FROM AUTHOR]

. 1. The effects of the current changes in traditional agricultural practices in the Alps on the biodiversity affecting ecosystem functions and services are little known. Vineyards are among the oldest anthropogenic environments of high cultural and natural value that shape the landscape of large areas in Central and Southern Europe. In several mountain regions of the Alps, vineyards are a valid alternative to the landscape homogenisation that has followed post-cultural land abandonment and agriculture intensification. Key unanswered questions remain regarding the relative contribution of several factors that influence biodiversity, and the level in management pressure with regard to taxonomic and functional diversity enhancement. 2. To answer these questions, we sampled leafhoppers (Auchenorrhyncha) as a model taxon using different standard techniques along 24 vine transects within 8 vineyard complexes in Southern Switzerland. Each transect included one vine row, vine canopy, its interrow and the adjacent slope; the latter two were permanently grass-covered. Data were analysed using a four-step approach. 3. Environment (five variables) and Management (four variables) accounted for most of the variance in the leafhopper assemblage. Pesticide use (insecticide and herbicide) and slope mowing are the most important management predictors of leafhopper species composition. 4. With increasing management pressure (i.e. pesticide and mowing), the number of indicator species and particularly the specialists (i.e. stenotopic and oligotopic species) decreases dramatically. 5. To promote taxonomic and functional complexity of communities in vineyard systems, we suggest low management pressure with moderate use of pesticide and a low intensity regime of slope mowing. [ABSTRACT FROM AUTHOR]

. 1. Livestock grazing impacts on insect populations in a variety of ways. For phytophagous insects the impact is primarily a result of altering the structure and species assemblage of vegetation. However not all species react in similar ways and even within an order there may be winners and losers from different grazing regimes. 2. A long-term, replicated, controlled experiment, comprising four grazing treatments, was established within an upland acid grassland area in Scotland. Auchenorrhyncha were sampled by suction sampling and sweep-netting in the fifth year following the start of the treatments. 3. A significant treatment effect was apparent in the suction samples with Auchenorrhyncha abundance being three to four times higher in the ungrazed plots compared to the other treatments. Abundance was also highest from the ungrazed plots in the sweep net samples, but this effect was not statistically significant. Redundancy analysis (RDA) showed that a suite of species which are typical of shaded positions responded with increased abundance in the ungrazed plots. 4. The findings demonstrate that the assemblages found in ungrazed areas can be vastly different to those found in even lightly grazed areas and therefore, underline the benefits of varied grazing regimes in maximising diversity. Furthermore, the work underlines the benefit of employing multiple sampling methods. [ABSTRACT FROM AUTHOR]

The article offers information on a study related to hilltopping in insects belonging to the subfamilies Myopinae and Dalmanniinae, which is behavior of males aggregating on a peak and mating with the females flying there. It further informs that several studies were previously conducted for studying hilltoping in species including Conopidae. It mentions that hilltoping is a strategy which is adopted for mate finding in insects which includes rare species or widely dispersed species.

An important hypothesis concerning the role of aggregation in the antipredator defense of aposematic insects is that a group projects a larger aposematic signal to a predator. The nearly exclusive use of birds as model predators may be leading us to over-emphasize the importance of signal amplification as an explanation for the gregarious behavior of aposematic insects. Ambush (sit-and-wait) predators such as amphibians and praying mantids make predatory decisions relying primarily on prey movement, and secondarily on prey size, with prey color being less important. Therefore, we tested the interaction of aposematic coloration and gregarious behavior in insect defense from frogs. We offered frogs four types of mealworm prey: (1) cryptic and solitary, (2) cryptic and gregarious, (3) aposematic and solitary, and (4) aposematic and gregarious. The frogs ate aposematic and gregarious prey significantly later than they ate cryptic and gregarious prey and cryptic and solitary prey. Our results support the hypothesis that aposematic coloration in gregarious prey, but not in solitary prey, can function to produce a sufficient aposematic signal to delay attack by an ambush predator. This result was not due to predator learning. Hence, the antipredator benefits of aposematic coloration in aggregated prey may function in encounters with a wide range of predators, including frogs. [ABSTRACT FROM PUBLISHER]

Ladybird beetles (Coleoptera: Coccinellidae) are predators of aphid and psyllid species and are often released or encouraged into timber plantations as natural enemies of economic pests. Some temperate coccinellid species overwinter in mass aggregations; however, little is known about coccinellid aggregations in Australia. Aggregations of Harmonia conformis were observed only on stone walls of a camp shelter near Shelley, Victoria in July 2014. Publication of more observational records and dedicated surveys will determine if old stone walls and buildings in managed landscapes have the potential to provide overwintering habitat for natural enemies and other beneficial insects. [ABSTRACT FROM AUTHOR]

We suggest that male aggregation in Euphydryas may be a side effect of their mate-finding behavior. Euphydryas males investigate any flying object that resembles a female and, as a result, spend much of their time chasing each other. Under some circumstances, this male-male chasing behavior can lead to the "incidental" formation of male aggregations. We tested our "incidental aggregation" hypothesis with a population of E. anicia that occurs on a flat plain, thereby eliminating topographical factors that may bias male movement. In three of four years the distribution of males was significantly aggregated. Observations of male movements indicate that when their flight is uninterrupted by encounters with other butterflies, males tend to follow highly directional straight paths. However, when they encounter other males, females, or even non-conspecifics, the directionality of their movement breaks down; that is, the direction of the flight after a chase is not correlated with the direction of the flight before the chase. Using a computer simulation, we show that the tendency of males to chase each other results in a clumped distribution of males. A behavior that is presumably adaptive-namely, to investigate all possible mates-therefore has an incidental effect on the pattern of male movement, resulting in the formation of male aggregations. [ABSTRACT FROM AUTHOR]

Many insect species form aggregations in either the larval or adult stage. The evolution of gregariousness in insects may seem disadvantageous because aggregations are easily discovered by a predator and because insects are small and slow in relation to many potential predators that then have the capacity to consume an entire group. For animals in general, a benefit of group living may be a decreased risk of predator attack on any particular individual. For insects, this effect, called dilution, can be a consequence of distastefulness, which limits the number of prey that a predator can take. A model is developed in which we vary the risk of detection in relation to group size and the degree of prey distastefulness and aposematic coloration, both of which affect the number of prey a predator samples during avoidance learning. According to the model, members of small groups may have a higher rate of death from predation than solitary individuals, but above a certain minimum group size, group members do better than solitary individuals. As group size increases above the minimum value, group members suffer fewer and fewer deaths from predation. However, other factors, unrelated to predation, constrain group size. For gregariousness to be advantageous, such constraints must be weak enough to allow groups larger than the minimum size. Our model predicts that (1) gregarious insect species should be distasteful, and the evolution of distastefulness should precede that of gregariousness; (2) the distribution of group sizes among species should show a bimodal form; and (3) the largest aggregations should be found in forms that have fewer constraints unrelated to predation on group size. The agreement between these predictions and data is discussed. [ABSTRACT FROM AUTHOR]

Densities of two allochronic, geographically overlapping populations of periodical cicadas were censused in the eggnest stage in order to test the hypothesis that larger populations can be supported when the root-feeding nymphs are of different ages. In a frequently burned chest-high stand of scrub oak (Quercus ilicifolia) on Long Island, Magicicada septendecim emerged in 1974 (Brood XIV), then again in 1978 (Brood I) from under the same individual plants over an area of about 1.2 x 3.5 km. Adjacent to this, in the same vegetation, periodical cicadas emerged in 1974 but not in 1978. A nested scheme of sampling revealed significantly higher total eggnest densities when Broods I and XIV occupied the same ground than when Brood XIV existed by itself. The major component of variation in density was among quadrats within plots. That is, cicadas exhibited patchiness on a small scale (metres) which was not reflected in patchiness on a larger scale (tens of metres). Microspatial distributions were thus patchy in both Brood I and XIV, yet dense patches of one brood were usually not correlated with dense patches of the other. Apparently the vegetation appears about as uniform to the cicadas as it does to the human observer, the primary cause of the patchy oviposition pattern being either mutual attraction among oviposition females or lack of dispersal from the chorusing and mating centers. The degree of patchiness is inversely density-dependent, in that the most patchy distributions were invariably those with lowest density. However, several plots with low density were not very patchy. This pattern makes biological sense, remembering that mutual attraction cannot operate unless the animals perceive one another, and at low densities they may sometimes do so and sometimes not. Further analysis, plotting mean crowding against mean density (following Iwao 1968) suggests that mutual attraction among females is weakened at high densities. As modes of data analysis, both kinds of plots-mean crowding vs. mean density and patchiness vs. mean density-bring out patterns that would not otherwise be apparent. In this connection, we offer an empirical definition for the concept, density-independent aggregation." [ABSTRACT FROM AUTHOR]

Spittlebugs are the vectors of the bacterium Xylella fastidiosa Wells in Europe, the causal agent of olive dieback epidemic in Apulia, Italy. Selection and distribution of different spittlebug species on host-plants were investigated during field surveys in 2016–2018 in four olive orchards of Apulia and Liguria Regions of Italy. The nymphal population in the herbaceous cover was estimated using quadrat samplings. Adults were collected by sweeping net on three different vegetational components: herbaceous cover, olive canopy, and wild woody plants. Three species of spittlebugs were collected: Philaenus spumarius L., Neophilaenus campestris (Fallén), and Aphrophora alni (L.) (Hemiptera: Aphrophoridae). Philaenus spumarius was the predominant species both in Apulia and Liguria olive groves. Nymphal stages are highly polyphagous, selecting preferentially Asteraceae Fabaceae plant families, in particular some genera, e.g., Picris, Crepis, Sonchus, Bellis, Cichorium, and Medicago. Host-plant preference of nymphs varies according to the Region and through time and nymphal instar. In the monitored sites, adults peak on olive trees earlier in Apulia (i.e., during inflorescence emergence) than in Liguria (i.e., during flowering and beginning of fruit development). Principal alternative woody hosts are Quercus spp. and Pistacia spp. Knowledge concerning plant selection and ecological traits of spittlebugs in different Mediterranean olive production areas is needed to design effective and precise control strategies against X. fastidiosa vectors in olive groves, such as ground cover modifications to reduce populations of spittlebug vectors. [ABSTRACT FROM AUTHOR]

Gregarious locust and solitary locust display significant differences in behavior, physiology, and morphology in response to the changes in population density. Here, we show that two phases also differ significantly in volatile composition and their emission dynamics along with the development and sexes. The body odors of the gregarious and solitary nymphs are mainly consisted of aromatic compounds, such as benzaldehyde, guaiacol, phenol, anisole, veratrole, and aliphatic acids (C2 and C6). PAN and 4-vinylanisole are present in gregarious locust, but are absent in solitary locust. These two compounds were completely lost in gregarious nymphs during solitarization process, but were obtained by solitary nymphs during gregarization. The amounts of benzaldehyde, guaiacol, and phenol only unidirectionally decreased from solitary to crowded treatment (see pages 60-72). Picture provided by Jianing Wei. [ABSTRACT FROM AUTHOR]

The challenges of maintaining cohesion while making collective decisions in social or aggregating insects can result in the emergence of a leader or leaders. Larval aggregations of the steel-blue sawfly Perga affinis forage nocturnally, and some larvae lead the aggregation on foraging trips more often than expected by chance. We investigated the relationship between these leader and follower roles by comparing the weight and growth of individual larvae with different roles. Our observations reveal no significant difference between the growth of leaders and followers, suggesting that the role of leadership may not provide direct foraging benefits. However, by experimentally manipulating the social structure of larval aggregations, we found that individuals within aggregations that comprise a mixture of leaders and followers enjoy higher growth rates than those in aggregations comprising a single behavioural type. These data demonstrate, for the first time, individual benefits to maintaining a balance of leader and follower roles within larval aggregations, and highlight the importance of considering the perspectives of both leaders and followers when investigating the evolutionary significance of this behavioural variation within animal groups. [ABSTRACT FROM AUTHOR]

The article summarizes the research paper "Nonlocal Aggregation Models: A Primer of Swarm Equilibria" by Andrew J. Bernoff and Chad M. Topaz. The paper is recognized for providing a clear account of very direct distinctions between Fredholm integral equations and apocalyptic plagues of locusts. Particular focus is given to the behavior of Schistocerca gregaria, the swarming desert locust in Africa.