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Katydids produce sound for signaling and communication by stridulation of the tegmina. Unlike crickets, most katydids are known to sing at ultrasonic frequencies. This has drawn interest in the investigation of the biophysics of ultrasonic sound production, detection, evolution, and ecology (including predator–prey interactions) of these katydids. However, most of these studies are based on species from the Neotropics, while little is known about katydid species from the hyperdiverse region of Southeast Asia. To address this, a concerted effort to document, record, and describe the calling songs of Southeast Asian katydids, especially species that call at ultrasonic frequencies, was made. A study spanning two years (2018–2020) in the Malay Peninsula (Singapore and Malaysia), Borneo (Brunei Darussalam and Sabah), and the Philippines revealed previously unknown calls of 24 katydid species from four subfamilies. The calling songs of Southeast Asian katydid species are highly diversified in terms of time and frequency. Call structure can range from isolated syllables (e.g., Holochlora), continuous trills (e.g., Axylus philippinus), to short pulse-trains (e.g., Euanisous teuthroides) and complex echemes (e.g., Conocephalus spp.), with 87.5% of species having ultrasonic peak frequencies and 12.5% being considered extreme ultrasonic callers (peak frequency >40 kHz). The call spectrum ranges from tonal (e.g., spectral entropy is 6.8 in Casigneta sp. 2) to resonant (entropy is 8.8 in Conocephalus cognatus). Of the 24 species whose calls are described here, we imaged and described the sound-producing structures of 18. This study provides a preliminary overview of the acoustic diversity of katydids in Southeast Asia, and the authors hope to inspire further investigation into the bioacoustics of little-known katydids from these areas. Amassing a database of calling songs and sound-producing organ illustrations from different species is important to address taxonomic impediments while advancing our knowledge about the bioacoustics of Southeast Asian katydids.

The propagation of animal vocalizations in water and in air is a well-studied phenomenon, but sound produced by bark and wood boring insects, which feed and reproduce inside trees, is poorly understood. Often being confined to the dark and chemically-saturated habitat of wood, many bark- and woodborers have developed stridulatory mechanisms to communicate acoustically. Despite their ecological and economic importance and the unusual medium used for acoustic communication, very little is known about sound production in these insects, or their acoustic interactions inside trees. Here, we use bark beetles (Scolytinae) as a model system to study the effects of wooden tissue on the propagation of insect stridulations and propose algorithms for their automatic identification. We characterize distance-dependence of the spectral parameters of stridulatory sounds, propose data-based models for the power decay of the stridulations in both outer and inner bark, provide optimal spectral ranges for stridulation detectability, and develop automatic methods for their detection and identification. We also discuss the acoustic discernibility of species cohabitating the same log. The species tested can be acoustically identified with 99% of accuracy at distances up to 20 cm and detected to the greatest extent in the 2-6 kHz frequency band. Phloem was a better medium for sound transmission than bark.

The aim of this review is to summarize the literature knowledge about how abiotic environmental factors and biotic interactions affect the sequentially overlapping longitudinal distribution of Central European species of the net-spinning freshwater caddisfly larvae of the genus Hydropsyche (Trichoptera: Hydropsychidae). In this relation, several physical and chemical parameters of water are discussed, as well as different species-specific traits, behavioural aspects and the interaction of coexisting species. Longitudinal gradients of river networks, especially annual temperature range, flow velocity and the particle size of suspended food material play a crucial role in forming the downstream succession of characteristic species, while increased levels of organic pollution, nutrients, salinity and heavy metals facilitates the presence of more tolerant ones. Several species-specific traits, such as respiration range, net-building frequency, head capsule size or optimal net-building velocity correlate with the position of a given species in the sequence. Coexistence of species with similar ecological demands in the overlapping zones of distribution is facilitated by differences in feeding and net-building habits, microhabitat preferences and staggering life cycles, but complicated at the same time by means of inter- and intraspecific territorial behaviour, such as fighting for the ownership of larval retreats or the practice of stridulation.

Cryptic animal species are often distinguishable by nonvisual communication signals used in specific-mate recognition. The three cryptic taxa comprising the Paragalago zanzibaricus species complex use distinct loud calls that do not obviously reflect molecular phylogenetic relationships. Paragalago granti and P. cocos both have incremental calls but are not sister taxa; P. cocos is the sister taxon to P. zanzibaricus, which has a rolling (trilling) call like that of P. rondoensis, one of the outliers to the complex. To test current hypotheses of species delimitation, I conducted 378 playback trials, using conspecific and heterospecific loud calls and recording both vocal responses and movement toward the speaker. To investigate the sensory drive hypothesis (acoustic adaptation), I measured reverberation duration of 215 short “yap” mobbing calls and examined 282 sonotopes (local soundscapes). I tested the hypothesis that different species’ ear lengths allow the animals to filter out interfering frequencies in local background noise. On Zanzibar Island, P. zanzibaricus responded solely to conspecific calls (23/32). In South Africa, P. granti individuals responded to conspecific calls (12/22) but also sometimes to P. cocos calls (9/22). In Kenya, P. cocos individuals responded to conspecific calls (34/40) but also sometimes to P. zanzibaricus calls (8/40). The three habitats showed differences in reverberation duration, and soundscapes differed in background orthopteran frequencies. Incremental calls probably evolved in the ancestor of the complex, in response to high levels of reverberation and a continuous backdrop of katydid stridulation in dry forest. Secondary evolution of trilling and decreased ear size probably evolved as result of decreased reverberation and higher frequency katydid interference in the P. cocos–P. zanzibaricus ancestor. A loss of short units in P. zanzibaricus probably occurred as result of decreased reverberation in thicket. The study validates the three species of the complex and provides information supporting speciation by sensory drive.

The importance of vision-reliant defensive traits (e.g. warning colours) in mimicry studies is well established, but their effectiveness is limited by visibility. In low light conditions, for instance, acoustic or tactile channels may be more effective. The juvenile and adult stages of the nocturnal hunting Palpimanus spiders audibly stridulate when harassed. Given this we hypothesized that the sound produced by Palpimanus has a defensive role against interspecific predators. Palpimanus though are poorly defended especially against something as large as a gecko. Hence we hypothesized that the stridulation is effective because the spider mimics co-occurring mutillid wasps. We staged predator feeding experiments in which mutillid wasps, sham-operated Palpimanus, silenced Palpimanus and a nonstridulating spider were offered to Eusparassus spiders and geckoes. Stridulating spiders had significantly greater survival against both predators than the nonstridulating treatments and comparable survival to the mutillid wasps. This result represents the first confirmed case of a spider using stridulation against an interspecific predator. Stridulation deterred Eusparasus spiders, while in geckoes stridulation acted postcapture as they dropped the prey instead of attempting to swallow them. For mutillid wasps this dropping response was typically more rapid than with Palpimanus but attempts to swallow silenced individuals were more frequent than sham-operated individuals, which were more likely to be dropped before any attempt to swallow. Analyses of stridulation characteristics of Palpimanus showed they were similar to acoustic signals of four of the co-occurring mutillid wasps and far more so than distress signals of control insects. Our study overall supports the notion that Palpimanus spiders are Batesian mimics of sympatrically occurring mutillids through the use of an aposematic acoustic signal and not just an example of a startle response.

The observable diversity of antipredator defences across organisms demonstrates predation's impact on trait evolution. The functions of many traits that are presumed to have an antipredator function have never been directly tested. The spiny orb-weaving spider, Micrathena gracilis, for example, stridulates when grasped. While stridulation was first hypothesized to be an antipredator defence nearly 50 years ago, no data exist to support this hypothesis. To explore the form and function of M. gracilis stridulation, we first quantified the behavioural and acoustical properties of sound production. Next, using laboratory assays, we directly tested the effect of stridulation on survival with an avian predator – blue jays, Cyanocitta cristata. Finally, we conducted a large mark–recapture field study in which we compared the natural survival of experimentally manipulated adult female M. gracilis that could not stridulate (silenced) versus could stridulate (control). Stridulatory pulses produced broadband frequency spectra, consistent with acoustic antipredator defences in other taxa. We also observed stridulation by male M. gracilis for the first time. In staged laboratory interactions with captive blue jays, we found no differences in survival between silenced and control M. gracilis. Similarly, in our mark–recapture field study, we found no differences in survival estimates between silenced and control groups, nor an effect of stridulation rate. While M. gracilis stridulation closely resembles antipredator stridulation in other arthropods, our behavioural data do not yet provide solid support for an antipredator function in M. gracilis.

The intertidal isopod Dynoides dentisinus is a sexually dimorphic species; males are much larger than females and have a large, horn-like pleonal process (hereafter referred to as a "horn") and large, posteriorly extended uropods. Here, we investigated the function of these structures with regard to their mating system. Behavioral interactions were observed between a male occupying a small tube (resident) and a newly introduced individual (a female or male visitor). When the visitor was male, the resident repeatedly struck the visitor with his horn; each swing was accompanied by a short sound produced by stridulation. The resident also used his uropods to strike the male visitor and then rejected the visitor. The resident struck the female visitor in a similar fashion but eventually accepted her into the tube; during this process, the resident frequently emitted stridulatory sounds. Our field survey found that the members shared a single shelter (barnacle shell) containing groups composed of several males and females. This suggests that the mating system of this species is polygynandry. The number of females in a single barnacle shell was positively associated with the basal diameter of the barnacle shell. However, the number of females was not associated with the body size, horn size, or uropod size of the largest male in the barnacle shell. These results suggest that male body size, horns, and uropods might have evolved as weapons through male-male competition for large barnacle habitats and more females, but that they have not evolved as ornaments via female choice.

Acoustic signals are an essential part of the multi-modal systems of conspecific communication among insects. The patterns of abiotic factors effects on their communication parameters are of great interest for prognostic purposes in current climatic instability and for practical application in order to manage their populations. The aim of this study was to reveal the dependence of the parameters of acoustic signals produced by bark beetle Polygraphus proximus, an aggressive alien stem pest on the environmental temperature. Male stridulatory signals were recorded in seven temperature settings (5–35 °C), and changes in their temporal parameters were evaluated under laboratory conditions. The obtained results allowed us to reveal the pattern of temperature dependence of signals produced by P. proximus. More than half of the insects were found to actively stridulate at 5 °C. Raising temperature caused an increment in chirp rate that continued to increase up to 30 °C. Further temperature increase led to suppression of signaling in most of the tested males. The obtained results showed a number of patterns of temperature effect on the parameters of acoustic signals which might be universal for representatives of different bark beetles genera with various stridulatory apparatus types.

Anthropogenic noise pollution is known to alter the behaviour of acoustically sensitive animals. Many animals also sense vibrations through solid substrates and use substrate-borne vibrations in conspecific communication. The effects of substrate-borne noise pollution, however, remain largely unknown. Here, we investigate the potential for seismic (soil-borne) noise to alter the reproductive behaviour of the burying beetle Nicrophorus marginatus, a species that breeds below the soil surface on vertebrate carcasses and provides biparental care to offspring. Nicrophorus marginatus beetles produce sound using stridulatory structures on the elytra and abdomen, but no ears have been identified in these beetles, suggesting that stridulation might function to produce substrate-borne signals. We examined the timing of stridulation during reproduction, measured neural responses of beetles to substrate-borne vibrations, and measured beetle reproduction in the presence and absence of seismic noise. We found that parental beetles stridulate throughout carcass preparation and the burial process and confirmed that adult beetles are sensitive to low-frequency seismic vibrations. Variables related to brood size were affected in treatments with seismic noise, with burying beetles producing smaller broods with lower total mass than those in control treatments, providing support for the hypothesis that substrate-borne noise may impose fitness costs for soil-dwelling animals. The precise mechanisms leading to reduced brood size remain unknown but may relate to disruption of seismic communication or inaccurate assessment of resource size. Additional investigations are required to understand the degree to which human-generated seismic noise in natural settings influences other edaphic species, and whether these behavioural impacts lead to shifts in edaphic community structure or function.

Hygrobiidae, or squeak beetles, originated in the Triassic-Jurassic and exhibit a relictual distribution in the Palaearctic, Oriental and Australasian regions. Hygrobiids are well known for their s...

Solifugae, also known commonly as sun spiders or camel spiders, are spider-like arachnid predators commonly present in desert and arid environments, though they also occur in forests and grasslands...

Signalling via substrate vibration represents one of the most ubiquitous and ancient modes of insect communication. In crickets (Grylloidea) and other taxa of tympanate Ensifera, production and detection of acoustic and vibrational signals are closely linked functionally and evolutionarily. Male stridulation produces both acoustic and vibrational signal components, the joint perception of which improves song recognition and female orientation towards the signaller. In addition to stridulation, vibrational signalling mainly through body tremulation and/or drumming with body parts on the substrate has long been known to be part of crickets' close-range communication, including courtship, mate guarding and aggression. Such signalling is typically exhibited by males, independently or in conjunction with stridulation, and occurs literally in all cricket lineages and species studied. It is further also part of the aggressive behaviour of females, and in a few cricket groups, females respond vibrationally to acoustic and/or vibrational signals from males. The characteristics and function of these signals have remained largely unexplored despite their prevalence. Moreover, the communication potential and also ubiquity of cricket vibrational signals are underappreciated, limiting our understanding of the function and evolution of the cricket signalling systems. By providing a concise review of the existing knowledge of cricket perception of vibrations and vibrational signalling behaviour, we critically comment on these views, discuss the communication value of the emitted signals and give some methodological advice respecting their registration and control. The review aims to increase awareness, understanding and research interest in this ancient and widespread signalling mode in cricket communication.

Bush-crickets (or katydids) of the genus Mecopoda are relatively large insects well-known for their sounds for centuries. Bioacoustic studies in India and China revealed a surprisingly large diversity of sound patterns. We extend these studies into the tropics of South East Asia using integrative taxonomy, combining song analysis, morphology of sound producing organs and male genitalia as well as chromosomes, to get a better understanding of the phylogeny and evolution of this widespread group. Besides the closely related genus Eumecopoda, the genus Mecopoda contains some isolated species and a large group of species which we assign to the Mecopoda elongata group. Some species of this group have broad tegmina and stridulatory files with different tooth spacing patterns and produce continuous, often relatively complicated, trill-like songs. The species of another subgroup with narrower wings have all similar files. Their songs consist of echemes (groups of syllables) which differ in syllable number and syllable repetition rate and also in echeme repetition rate. Our results show that South East Asia harbours a large and certainly not yet fully explored number of Mecopoda species which are most easily and clearly identified by song. Based on the data, five new forms are described: Mecopoda mahindai Heller sp. nov., Mecopoda paucidens Ingrisch, Su & Heller sp. nov., Mecopoda sismondoi Heller sp. nov., Mecopoda niponensis vietnamica Heller & Korsunovskaya subsp. nov., Eumecopoda cyrtoscelis zhantievi Heller subsp. nov. In addition, some taxonomic changes are proposed: Eumecopoda Hebard, 1922 stat. rev., Paramecopoda Gorochov, 2020, syn. nov. of Eumecopoda Hebard, 1922, Mecopoda javana (Johansson, 1763) stat. nov. (neotype selected) with M. javana minahasa Gorochov, 2020 stat. nov., M. javana darevskyi Gorochov, 2020 stat. nov., M. javana buru Gorochov, 2020 stat. nov., Mecopoda macassariensis (Haan, 1843) stat. rev., Mecopoda ampla malayensis Gorochov, 2020 syn. nov., Mecopada ampla javaensis Gorochov, 2020 syn. nov., Mecopoda fallax aequatorialis Gorochov, 2020 syn. nov., the last three are all synonyms of Mecopoda himalaya Liu, 2020, Mecopoda yunnana Liu 2020, stat. nov.

Blue catfish Ictalurus furcatus, the largest catfish in North America and an invasive species in Chesapeake Bay estuaries, has experienced explosive population growth, negatively impacting native species. They have strong pectoral spines that can be locked and rubbed against the pectoral girdle to produce stridulation sounds although sound production during behavioral interactions is unstudied. We examined agonistic behavior in juveniles by allowing individuals to establish a territory and introducing an intruder. Big (43–50 cm total length) and small (36–41 cm) fish were paired within and across size ranges. Territory was considered established when a fish remained in its shelter for over an hour. Fish typically entered the shelter head first and maintained that orientation. They used a variety of agonistic behaviors in shelter defense including aggressive contact, caudal sweeping, and standoff but not the production of stridulation sounds. Individuals often utilized different behaviors indicating less stereotypy than in many fishes, and there were differences in incidence of behaviors between big and small fish. Residents and larger fish did not always win, perhaps due to juvenile status and low fitness consequences of territorial possession.

Stridulation is a type of communication in which a mechanical signal is emitted by the friction of two rigid structures. Stridulation is present in kissing bugs (Reduviidae: Triatominae), where the...

Male Katydids (Orthoptera: Tettigoniidae) rub together their specialised forewings to produce sound, a process known as stridulation. During wing closure, a lobe on the anal margin of the right forewing (a scraper), engages with a teeth-covered file on the left forewing. The movement of the scraper across the file produces vibrations which are amplified by a large wing cell adjacent to the scraper, the mirror. Katydids are known to stridulate with either sustained or interrupted sweeps of the file, generating resonant pure-tone (narrowband frequency) or non-resonant (broadband frequencies) calls. However, some species can conserve some purity in their calls despite incorporating discrete pulses and silent intervals. This mechanism is exhibited by many Pseudophyllinae, such as Nastonotus spp., Cocconotus spp., Triencentrus spp. and Eubliastes spp. This study aims to measure and quantify the mechanics of wing stridulation in Nastonotus foreli, a Neotropical katydid that can produce complex, relatively narrowband calls at ≈20kHz. It was predicted that this species will use a stridulatory mechanism involving elastic energy whereby the scraper bends and flicks along the file in periodic bursts. The calling behaviour and wing mechanics of seven males were studied using a combination of technologies (e.g. micro-scanning laser Doppler vibrometry, advanced microscopy, ultrasound-sensitive equipment and optical motion detectors) to quantify wing mechanics and structure. Analysis of recordings revealed no clear relationship between wing velocity and carrier frequency, and a pronounced distinction between wing velocity and scraper velocity during wing closure, suggesting that the scraper experiences considerable deformation. This is characteristic of the elastic scraper mechanism of stridulation. Curiously, N. foreli might have evolved to employ elastic energy to double the duration of the call, despite possessing muscles that can reach velocities high enough to produce the same frequency without the help of elastic energy.

This review addresses the history of neuroethological studies on acoustic communication in insects. One objective is to reveal how basic ethological concepts developed in the 1930s, such as innate releasing mechanisms and fixed action patterns, have influenced the experimental and theoretical approaches to studying acoustic communication systems in Orthopteran insects. The idea of innateness of behaviors has directly fostered the search for central pattern generators that govern the stridulation patterns of crickets, katydids or grasshoppers. A central question pervading 50 years of research is how the essential match between signal features and receiver characteristics has evolved and is maintained during evolution. As in other disciplines, the tight interplay between technological developments and experimental and theoretical advances becomes evident throughout this review. While early neuroethological studies focused primarily on proximate questions such as the implementation of feature detectors or central pattern generators, later the interest shifted more towards ultimate questions. Orthoptera offer the advantage that both proximate and ultimate questions can be tackled in the same system. An important advance was the transition from laboratory studies under well-defined acoustic conditions to field studies that allowed to measure costs and benefits of acoustic signaling as well as constraints on song evolution.

On the basis of the song and morphological analyses, we revised the status of the subspecies Stenobothrus eurasius eurasius Zubowsky, 1898, and S. eurasius hyalosuperficies Vorontsovskii, 1927. The status of the subspecies S. eurasius hyalosuperficies Vor. has been changed to the species level. The most striking difference between S. eurasius and S. hyalosuperficies lies in the song parameters. The calling songs differ not only in temporal parameters but are also produced by different mechanisms. S. eurasius generates calling songs by common leg stridulation, whereas S. hyalosuperficies produces sound by wing clapping. The courtship songs of both species are complex (contain several elements) and very different in temporal structure. The morphological differences between the two species are not as striking as the differences in bioacoustics: we found the only differences in the hind wing venation. At the same time, we suggest these differences to be important since they might be due to different mechanisms of sound production. We revised the ranges of the two species on the territory of Ukraine, Russia and Kazakhstan. We also reviewed the type localities of S. eurasius Zub. and designated lectotype and paralectotype of this species.

The family Theraphosidae is the most speciose in the infraorder Mygalomorphae Pocock, 1892 with over one thousand described species (World Spider Catalog 2021). The taxonomy of the group has been subjected to considerable attention in modern times, with a focus on delineation based predominantly on genital organ and stridulatory organ morphology which has shown promise, both alongside molecular methods (where possible) and as a stand-alone line of evidence, in stabilising the group (e.g. Hamilton et al. 2016; Fabiano-da-Silva et al. 2020; see also Sherwood 2020). The predominant reference to the family is as Theraphosidae Thorell, 1870 with almost as many references to Theraphosidae Thorell, 1869. This non-congruence of dates is because Tord Tamerlan Teodor Thorell (1830–1901) had his important work On European Spiders published in two parts during its publication by the Royal Society of Upsala in its journal Nova Acta Regiae Societatis Scientiarum Upsaliensis. The first half (pages 1–108 and the supplement I–XIII) was published in 1869 whereas pages 109–242 (despite being dated on the cover page as 1869) were published in 1870 (see Roewer 1942; Bonnet 1945; World Spider Catalog 2021). In the second part, the secretary of the society notes: “L’auteur avait proposé comme titre du présent mémoire: Remarks on Synonyms of European Spiders, preceded by some observations on Zoological Nomenclature and a Review of the European Genera of Spiders; mais, la partie, insérée dans le Tome VII, étant seule présentée à la Société des Sciences le 13 Fevr. 1869, il a été nécessaii’e d’y conformer le titre.” [= The author proposed as the title of this memoir: Remarks on Synonyms of European Spiders, preceded by some observations on Zoological Nomenclature and a Review of the European Genera of Spiders; but, the part, inserted in Volume VII, being the only one presented to the Société des Sciences on 13 Feb. 1869, it was necessary to conform the title to it.].

Synopsis There are at least eight ways that wings potentially produce sound. Five mechanisms are aerodynamic sounds, created by airflow, and three are structural sound created by interactions of solid surfaces. Animal flight is low Mach (M), meaning all animals move at

Insect defense sounds have been reported for centuries. Yet, aside from the well-studied anti-bat sounds of tiger moths, little is understood about the occurrence, function, and evolution of these sounds. We define a defense sound as an acoustic signal (air- or solid-borne vibration) produced in response to attack or threat of attack by a predator or parasitoid and that promotes survival. Defense sounds have been described in 12 insect orders, across different developmental stages, and between sexes. The mechanisms of defensive sound production include stridulation, percussion, tymbalation, tremulation, and forced air. Signal characteristics vary between species, and we discuss how morphology, the intended receiver, and specific functions of the sounds could explain this variation. Sounds can be directed at predators or non-predators, and proposed functions include startle, aposematism, jamming, and alarm, although experimental evidence for these hypotheses remains scant for many insects. The evolutionary origins of defense sounds in insects have not been rigorously investigated using phylogenetic methodology, but in most cases it is hypothesized that they evolved from incidental sounds associated with non-signaling behaviors such as flight or ventilatory movements. Compared to our understanding of visual defenses in insects, sonic defenses are poorly understood. We recommend that future investigations focus on testing hypotheses explaining the functions and evolution of these survival sounds using predator-prey experiments and comparative phylogenetics.

Melolonthinae are the largest subfamily of Scarabaeidae, considered as serious pests for their larvae attacking plant roots and tubers. The edaphic larvae are difficult to be identified because the study on larval taxonomy is far from satisfactory. In this study, multivoltine white grubs Melolontha incana (Motschulsky, 1853) were investigated using light and scanning electron microscopy, in order to provide more morphological characters for the pest identification. The white grubs are atypical for the epipharynx bearing 14 heli arranged in two rows; the mandible is furnished with a patch of minute granules; the maxilla is equipped with 18 acute stridulatory teeth arranged in line; each femur and tibiotarsus is furnished ventrally with a cluster of fossorial setae. The morphological comparisons with the other melolonthine species were provided. The adaptative relationship between the morphological feature and the multivoltine life history were briefly discussed.

The tettigoniid subfamily Phyllophorinae, distributed in Southeast Asia and Australia, is poorly known. Our study of the biology of Giant Katydid Siliquofera grandis (Blanchard, 1853) from a laboratory culture has shown that these insects mate more than once, the females lay a total of up to 400 eggs during their life, and these hatch after 2–2.5 months. The life cycle from egg to death takes longer than one year. In the laboratory, the insects fed mainly on leaves of various Rosaceae, Ficus, and lettuce, and on fruits. It is known that the males of hooded katydids lack the tegminal stridulatory apparatus typical for Tettigoniidae, but are capable of producing protest sounds using their coxosternal sound-producing organs for stridulation. Here, protest stridulation of the males and females and the sound-producing organs used to produce it have been analyzed in Phyllophorina kotoshoensis Shiraki, 1930 and S. grandis. In addition, nymphal protest sounds produced by friction of the metafemur against the edge of the pronotum and adult protest signals produced with the wings are described. In S. grandis, vibratory signals have been described and studied for the first time: territorial, protest, drumming and rhythmic low-amplitude vibrations emitted by adults and nymphs and pre- and postcopulatory vibrations of the males and females. The territorial signals not accompanied with visible movements of the body may be produced by contracting the antagonist muscles of the thorax and possibly of the legs. Using their coxosternal sound-producing organs males of S. grandis produced also an audible courtship song lasting for several seconds. Acoustic signals may thus both regulate intrapopulation relations and serve for interspecific communication (protest signals). The acoustic communication in Phyllophorinae is probably especially important during mating behavior.

Katydids from the subfamily Meconematinae sing at ultrasonic frequencies. Owing that many of them are nocturnal, elusive and low in abundance (since they are predatory), there is a dearth of information on these katydids and their bioacoustics, especially for species in the understudied yet mega-diverse Southeast Asia. Recent orthopteran surveys in Laguna, Luzon Island in the Philippines led to the discovery of two interesting Meconematinae katydids. Based on the collection, we describe a new species of Phisidini: Neophisis (Indophisis) montealegrei sp. nov. We also describe the male for the first time and redescribe the female of Asiophlugis philippina. The ultrasonic calling songs of both Meconematinae are also recorded, analysed and described here.

The capability of producing sounds and vibrations is well known in insects and is thought to be a form of intra- and interspecific communication. Sounds and vibrations are used and modulated for several aims such as interacting with conspecifics, getting information from the environment, and defending against predators. This phenomenon is less known but also present in other arthropods, including a few roller-type terrestrial isopods. In this study, we used a Y-shape test apparatus to investigate the behavior of adult individuals ofArmadillo officinalisDuméril, 1816 (Crustacea: Isopoda: Oniscidea) when exposed to two particular vibrational stimuli, namely species-specific stridulations and non-specific substrate-borne vibrations. Our results showed that adults ofA. officinalissignificantly react to the presence of both types of vibrational stimuli, by moving away from the vibrational source as if they experienced these vibrations as a sign of danger or disturbance.A. officinaliscan produce stridulations only when it rolls into a ball during the so-called conglobation, a possible defense mechanism against predators. Stridulation might thus be a secondary form of defense used during conglobation to deter a predator following contact with it and might be experienced as an alert by conspecifics nearby. The high sensitivity to non-specific substrate-borne vibrations might provideA. officinaliswith the possibility to anticipate dangers and adverse conditions, giving it a better chance of survival.

The communication between leaf-cutting ants occurs through chemical interactions and sound, which are important processes in the complex social system of these organisms. Studies have focused on the characterization and importance of stridulation and vibration of the substrate for ants in general. However, for leaf-cutting ant species, little information is available about the characterization and the function of vibration of the substrate during preparation and incorporation of plant material into the symbiotic fungus by workers. Therefore, the objective of the present study was to describe the vibration in Eucalyptus leaves generated by the stridulation of Atta laevigata (Smith) workers during processing and incorporation of the plant material into the symbiotic fungus, and to discuss its possible function. Vibrational signals were recorded with a laser vibrometer. The amplitudes of the emitted signals varied according to the behaviors performed, that is, each behavior showed a characteristic amplitude. Thus, the vibration in the leaves probably can aid in the efficiency of these ants during the processing of the vegetal material for the incorporation in its symbiont.Vibração do substrato vegetal gerada pela estridulação de operárias durante o cultivo do fungo em Atta laevigata (Smith) (Hymenoptera: Formicidae)Resumo. A comunicação entre as formigas cortadeiras ocorre por meio da interação química e do som, processos importantes no complexo sistema social destes organismos. Existem vários estudos enfocando a caraterização e a importância da estridulação e vibração do substrato para as formigas em geral. Contudo, pouco se tem descrito para as espécies de formigas cortadeiras sobre a caracterização e função da vibração do substrato durante o preparo e a incorporação do material vegetal pelas operárias no fungo simbionte. Assim, o presente trabalho descreveu a vibração nas folhas de Eucalyptus sp. gerada pela estridulação das operárias de Atta laevigata (Smith) durante o processamento e incorporação destas folhas no fungo simbionte, além de interpretar sua possível função. Os sinais vibratórios foram gravados com um vibrômetro a laser. As amplitudes dos sinais emitidos variaram conforme os comportamentos executados, ou seja, cada comportamento apresentou uma amplitude característica. Desse modo, a vibração nas folhas provavelmente pode auxiliar na eficiência dessas formigas durante o processamento do material vegetal para a incorporação no seu simbionte. Abstract. The communication between leaf-cutting ants occurs through chemical interactions and sound, which are important processes in the complex social system of these organisms. Studies have focused on the characterization and importance of stridulation and vibration of the substrate for ants in general. However, for leaf-cutting ant species, little information is available about the characterization and the function of vibration of the substrate during preparation and incorporation of plant material into the symbiotic fungus by workers. Therefore, the objective of the present study was to describe the vibration in Eucalyptus leaves generated by the stridulation of Atta laevigata (Smith) workers during processing and incorporation of the plant material into the symbiotic fungus, and to discuss its possible function. Vibrational signals were recorded with a laser vibrometer. The amplitudes of the emitted signals varied according to the behaviors performed, that is, each behavior showed a characteristic amplitude. Thus, the vibration in the leaves probably can aid in the efficiency of these ants during the processing of the vegetal material for the incorporation in its symbiont.Vibração do substrato vegetal gerada pela estridulação de operárias durante o cultivo do fungo em Atta laevigata (Smith) (Hymenoptera: Formicidae)Resumo. A comunicação entre as formigas cortadeiras ocorre por meio da interação química e do som, processos importantes no complexo sistema social destes organismos. Existem vários estudos enfocando a caraterização e a importância da estridulação e vibração do substrato para as formigas em geral. Contudo, pouco se tem descrito para as espécies de formigas cortadeiras sobre a caracterização e função da vibração do substrato durante o preparo e a incorporação do material vegetal pelas operárias no fungo simbionte. Assim, o presente trabalho descreveu a vibração nas folhas de Eucalyptus sp. gerada pela estridulação das operárias de Atta laevigata (Smith) durante o processamento e incorporação destas folhas no fungo simbionte, além de interpretar sua possível função. Os sinais vibratórios foram gravados com um vibrômetro a laser. As amplitudes dos sinais emitidos variaram conforme os comportamentos executados, ou seja, cada comportamento apresentou uma amplitude característica. Desse modo, a vibração nas folhas provavelmente pode auxiliar na eficiência dessas formigas durante o processamento do material vegetal para a incorporação no seu simbionte.

The North American vinegaroon, Mastigoproctus giganteus (Lucas, 1835), is demonstrated to comprise a complex of range-restricted species rather than a single widespread polymorphic species. Seven species are recognized based on morphological characters of the adult males, including the arrangement of spines on the prodorsal margin of the pedipalp trochanter, the position of the epistoma on the carapace, the presence of a stridulatory organ on opposing surfaces of the chelicerae and the pedipalp coxa, the presence of a patch of setae on sternite V, and the shape and macrosculpture of the retrolateral surface of the pedipalp femur. The two currently recognized subspecies are elevated to species: Mastigoproctus mexicanus (Butler, 1872), stat. nov., and Mastigoproctus scabrosus (Pocock, 1902), stat. nov. Mastigoproctus floridanus (Lonnberg, 1897) is revalidated from synonymy with M. giganteus. Redescriptions of M. giganteus and the other three species, based on both sexes, are provided, and three new species described: Mastigoproctus cinteotl, sp. nov., from Tamaulipas, Mexico; Mastigoproctus tohono, sp. nov., from Arizona and Sonora, Mexico; Mastigoproctus vandevenderi, sp. nov., from Sonora, Mexico. The present contribution raises the diversity of the Order Thelyphonida Latreille, 1804, in North America from one species to seven. Three species occur in the United States (one each in Arizona, Texas, and Florida), six species occur in Mexico, and two species occur in both countries.

Leafcutter ants communicate with the substrate-borne component of the vibratory emission produced by stridulation. Stridulatory signals in the genus Atta have been described in different behavioural contexts, such as foraging, alarm signalling and collective nest building. Stridulatory vibrations are employed to recruit nestmates, which can localize the source of vibration, but there is little information about the underlying mechanisms. Our experiments reveal that time-of-arrival delays of the vibrational signals are used for tropotactic orientation in Atta sexdens. The detected time delays are in the same range as the time delays detected by termites. Chemical communication is also of great importance in foraging organization, and signals of different modalities may be combined in promoting the organization of collective foraging. Here we show that the tropotactic orientation to vibrational signals interacts with chemical communication signals., Summary: Leafcutter ants communicate via substrate vibrations. Here we show that time delays between legs are used for orientation in a foraging context and that alarm pheromones interfere by changing the social context.

Electron scanning, photography and description of organs involved in stridulation were performed, for two selected species, for the first time globaly and particularly in Egypt. Male and female fresh specimens of Calephorus compressocornis (Latreille) and Truxalis grandis Klug (Acrididae: Acridinae) were collected and structures concerned in stridulation were scanned using scanning electron microscope (SEM), following standard techniques. The present investigations were carried out to achieve comparative studies, for organs and mechanisms concerning mechanical sound production (stridulation) of the two species. These two concerned species demonstrate two genera, each as a sole genus of its tribe. Calephorini and Truxalini, belonging to subfamily Acridinae (Acrididae), as distinct taxonomic groups, related taxonomically and varied distinctly in the stridulation and associated structure. Diagnosis and morphological characterization of the species, including their stridulatory apparatus are presented. Digital photos and scanning electron photography of the specialized parts concerning stridulation were also provided. In addition, their distribution and proposed stridulatory mechanisms were discussed. Moreover, extra structures (hind wings) were scanned by SEM, for any supposed structures.

Simple Summary Sexual selection influences a broad range of morphological, behavioral, and physiological characteristics, helping to drive the divergence of populations, up to and including the formation of new species. However, we are still limited in our ability to predict what traits sexual selection may favor and under what circumstances. We addressed sexual selection in the Hemiptera, also known as true bugs, identifying four main forms of sexual communication used by the sub-order Heteroptera (chemical signals, acoustic signaling via stridulation, abdominal vibration, and tactile signaling via antennation). We compared how these modes of sexual communication occur within three broad habitat types in which they are found (leaf-litter, plant-based, and semi-aquatic habitats), reviewing each mode of communication, their environmental context, and providing a wide range of examples of their occurrence within the Heteroptera. We argue that looking for associations between mechanisms of sexual selection and particular ecologies will help us move towards a more predictive theory of sexual selection. In our rapidly changing world, these kinds of studies may also be important in understanding the role sexual selection will play in determining species persistence. Abstract Sexual selection is a major evolutionary process, shaping organisms in terms of success in competition for access to mates and their gametes. The study of sexual selection has provided rich empirical and theoretical literature addressing the ecological and evolutionary causes and consequences of competition for gametes. However, there remains a bias towards individual, species-specific studies, whilst broader, cross-species comparisons looking for wider-ranging patterns in sexual selection remain uncommon. For instance, we are still some ways from understanding why particular kinds of traits tend to evolve under sexual selection, and under what circumstances. Here we consider sexual selection in the Heteroptera, a sub-order of the Hemiptera, or true bugs. The latter is the largest of the hemimetabolous insect orders, whilst the Heteroptera itself comprises some 40,000-plus described species. We focus on four key sexual signaling modes found in the Heteroptera: chemical signals, acoustic signaling via stridulation, vibrational (substrate) signaling, and finally tactile signaling (antennation). We compare how these modes vary across broad habitat types and provide a review of each type of signal. We ask how we might move towards a more predictive theory of sexual selection, that links mechanisms and targets of sexual selection to various ecologies.

Living organisms experience a worldwide continuous increase in artificial light at night (ALAN), negatively affecting their behaviour. The field cricket, an established model in physiology and behaviour, can provide insights into the effect of ALAN on insect behaviour. The stridulation and locomotion patterns of adult male crickets reared under different lifelong ALAN intensities were monitored simultaneously for five consecutive days in custom-made anechoic chambers. Daily activity periods and acrophases were compared between the experimental groups. Control crickets exhibited a robust rhythm, stridulating at night and demonstrating locomotor activity during the day. By contrast, ALAN affected both the relative level and timing of the crickets' nocturnal and diurnal activity. ALAN induced free-running patterns, manifested in significant changes in the median and variance of the activity periods, and even arrhythmic behaviour. The magnitude of disruption was light intensity dependent, revealing an increase in the difference between the activity periods calculated for stridulation and locomotion in the same individual. This finding may indicate the existence of two peripheral clocks. Our results demonstrate that ecologically relevant ALAN intensities affect crickets’ behavioural patterns, and may lead to decoupling of locomotion and stridulation behaviours at the individual level, and to loss of synchronization at the population level.

Three new hahniid species, Hahnia quadriseta sp. nov., Neoantistea multidentata sp. nov. and N. aspembira sp. nov., are described from a total of 1,131 individuals collected during spider inventories in Veracruz, Mexico. All specimens were collected inside four plots of Quercus forest, from leaf litter using active searching, sifted litter processed with Berlese funnels and pitfall traps. Sexual behavior and the natural history of N. aspembira sp. nov. are analyzed. In addition, the stridulatory organ morphology of both Neoantistea species is described. Stridulatory organs are absent in Hahnia quadriseta sp. nov., although present in other species of this genus. More information regarding this inventory and additional views of specimens can be found online at http://www.unamfcaracnolab.com

Acoustic communication is taxonomically widespread in bark beetles and is proposed to play an important role in a variety of social and defensive behavioural contexts. Yet our understanding of how signals vary between contexts is currently limited. The present study tests the hypothesis that acoustic signals vary between behavioural contexts in the female pine engraver beetle Ips pini (Say) (Coleoptera: Curculionidae: Scolytinae). Female Ips pini produce acoustic chirps using a vertex-pronotal stridulatory organ. Randomly sampled chirps generated under three contexts (i.e. distress, predation and premating) are compared for their duration, number of pulses, interpulse intervals, pulse rate and amplitude envelope shapes. The results obtained show that, during premating events, chirps are significantly longer in duration and tend to have a higher proportion of descending amplitude envelopes than chirps occurring during distress and predation events. Chirps produced during distress and predation conditions are indistinguishable from one another. By contrast to the results from previous bark beetle studies, no support is found for categorizing chirps as ‘interrupted’ or ‘uninterrupted’ types based on temporal patterns. The functional significance of context-dependent variation in chirp characteristics is discussed. Previous studies on acoustic communication in bark beetles are limited as a result of a general lack of objective sampling and measurement criteria for characterizing signals. Recommendations are outlined for future studies on the functions and evolution of acoustic communication in bark beetles.

In katydids (Orthoptera: Tettigonioidea) of the subfamily Phaneropterinae females ready to mate initiate a duet, announcing her position to the male singer, but also potentially to eavesdropping rivals. In many species the male seems to defend the communication by adding self-produced imitations of a female response. If these signals occur within the male sensory time-window after the female song, they can disturb the orientation of rivals. In two species of the genus Gonatoxia, males and females use short, relatively narrow-banded sounds (width 2–7 kHz 10 dB below peak). Male song and female response, however, differ considerably in peak frequency. In G. maculata, the peak frequency of the last part of the male song (13 kHz) is between that of the first part (15 kHz) and the female response (9 kHz), in G. helleri the last part (9 kHz; assumed imitation) and the female song are identical in peak frequency and by a factor two lower than the first part (19 kHz). The male stridulatory file of this species is correspondingly modified and differs from all other members of the genus. The imitation of spectral properties of the female response is not known from any other katydid.

In the hind wings of Yponomeuta and related genera there are transparent patches without scales; within these are arrays of ridges and it is suggested these may be used to produce sounds, with the adjacent membrane acting as a resonator. Avenues for further research are explored, together with potential taxonomic implications.

The water scavenger beetle tribe Hydrobiusini contains 47 species in eight genera distributed worldwide. Most species of the tribe are aquatic, although several species are known to occur in waterfalls or tree mosses. Some members of the tribe are known to communicate via underwater stridulation. While recent morphological and molecular-based phylogenies have affirmed the monophyly of the tribe as currently circumscribed, doubts remain about the monophyly of included genera. Here we use morphological and molecular data to infer a species-level phylogeny of the Hydrobiusini. The monophyly of the tribe is decisively supported, as is the monophyly of most genera. The genus Hydrobius was found to be polyphyletic, and as a result the genus Limnohydrobius stat. rev. is removed from synonymy with Hydrobius, yielding three new combinations: L. melaenus comb.n., L. orientalis comb.n., and L. tumbius comb.n. Recent changes to the species-level taxonomy of Hydrobius are reviewed. The morphology of the stridulatory apparatus has undergone a single remarkable transformation within the lineage, from a simple, unmodified pars stridens to one that is highly organized and complex. We present an updated key to genera, revised generic diagnoses and a list of the known distributions for all species within the tribe.

We investigated brain regions – mostly neuropils – that process auditory information relevant for the initiation of response songs of female grasshoppers Chorthippus biguttulus during bidirectional intraspecific acoustic communication. Male-female acoustic duets in the species Ch. biguttulus require the perception of sounds, their recognition as a species- and gender-specific signal and the initiation of commands that activate thoracic pattern generating circuits to drive the sound-producing stridulatory movements of the hind legs. To study sensory-to-motor processing during acoustic communication we used multielectrodes that allowed simultaneous recordings of acoustically stimulated electrical activity from several ascending auditory interneurons or local brain neurons and subsequent electrical stimulation of the recording site. Auditory activity was detected in the lateral protocerebrum (where most of the described ascending auditory interneurons terminate), in the superior medial protocerebrum and in the central complex, that has previously been implicated in the control of sound production. Neural responses to behaviorally attractive sound stimuli showed no or only poor correlation with behavioral responses. Current injections into the lateral protocerebrum, the central complex and the deuto-/tritocerebrum (close to the cerebro-cervical fascicles), but not into the superior medial protocerebrum, elicited species-typical stridulation with high success rate. Latencies and numbers of phrases produced by electrical stimulation were different between these brain regions. Our results indicate three brain regions (likely neuropils) where auditory activity can be detected with two of these regions being potentially involved in song initiation.

Eremocantor marioni, gen. nov. et sp. nov. is described for an unusual species of stridulating darkling beetle discovered in West Texas, USA. Stridulation in other members of the tribe Edrotini (Tenebrionidae: Pimeliinae) is discussed, including Edrotes LeConte and the previously unrecognized sound producing genera Pimeliopsis Champion, Pescennius Champion, Trichiotes Casey, and Oxygonodera Casey. A key to the known stridulating edrotine genera is also provided.

Despite growing evidence that crustaceans produce and detect sounds, the behavioural and biological function of these sounds is still poorly understood. Here, we describe sounds produced by the New Zealand paddle crab, Ovalipes catharus, and provide evidence of intraspecific communication using underwater sound. Acoustic and video analyses of tank-based experiments show that O. catharus produce at least three distinct sounds: the rasp, zip and bass. Notably, two of these sounds, the zip and bass, were directly correlated with post-copulatory mate-guarding and courtship behaviour and produced only by competing adult male crabs in the presence of a receptive female. Rasp sounds were produced by both sexes; the occurrence significantly increased in the presence of food, and play-back experiments of these sounds initiated a foraging-like behaviour. Responses to rasps might have evolved as a result of acoustic spying. Further, we show that both the rasp and bass sounds were produced by an alternative mechanism than stridulation of the chela ridges. This refutes widespread assumptions that Ovalipes crabs use only stridulation of ridges along their chelae to produce rasp-like sounds. Our results suggest that sound production in decapod crustaceans may be more widespread than previously presumed.

Root-feeding Scarabaeidae larvae can pose a serious threat to agricultural and forest ecosystems, but many details of larval ecology are still unknown. We developed an acoustic data analysis method based on active sound production by larvae (i.e. stridulations) for gaining new insights into larval ecology. In a laboratory study, third instar larvae of the Common Cockchafer (Melolontha melolontha) (n = 38) and the Forest Cockchafer (M. hippocastani) (n = 15) kept in soil-filled containers were acoustically monitored for 5 min each, resulting in the first known stridulation recordings for each species. Subsequent continuous monitoring of three M. hippocastani larvae over several hours showed that a single larva could stridulate more than 70 times per hour, and stridulation rates increased drastically with increasing larval abundance. The new fractal dimension-based data analysis method automatically detected audio sections with stridulations and provided a semi-quantitative estimate of stridulation activity. It is the first data analysis method specifically targeting Scarabaeidae larvae stridulations in soils, enabling for the first time non-invasive species-specific pest monitoring.

Cerambycidae is one of the largest families of beetles, containing about 38,000 described species (Tavakilian & Chevillotte 2018). In most species of this family, adults possess a stridulatory device that allows them to produce squeaking sounds (Wang 2017). In the subfamilies Prioninae and Parandrinae, individuals stridulate by rubbing their ridged hind femora against elytral margins (Švácha & Lawrence 2014). In the other subfamilies, including Lamiinae, the stridulation is produced by friction between the ventral face of the posterior pronotal margin (plectrum) and a striated plate on the mesoscutum (pars stridens) (Švácha & Lawrence 2014). Although some adults produce sounds during courtship and copulation, this sound production occurs mainly when individuals are disturbed, being considered a defensive mechanism that might act as a startle response against predators (Dumortier 1963; Švácha & Lawrence 2014; Wang 2017).

Asian genera and species of the plant bug tribe Hallodapini are reviewed. The present classification system is based particularly on detailed morphology and function of the stridulatory device and concealed habitat preference. Our recent efforts successfully demonstrated that the stridulatory devices of the forewing edge and dorsal metafemur are doubtlessly used for intraspecific communication (at least for courtship behavior). Based on the stridulatory structures and additional characters, Cleotomiris Schuh, 1995, Cleotomiroides Schuh, 1984, Hallodapus Fieber, 1858 and Wygomiris Schuh, 1984, are re-diagnosed and discussed; Alloeomimella Yasunaga & Duwal gen. nov. is proposed to accommodate Alloeomimus muiri Schuh, 1984 and a new combination, Alloeomimella muiri (Schuh) comb. nov., is accordingly established. Six new species are further described: Cleotomiroides ishikawachui Yasunaga & Duwal sp. nov. (Indonesia: Java); Hallodapus jingfui Yasunaga & Duwal sp. nov. (Taiwan); H. spinosus Yasunaga & Duwal sp. nov. (Thailand); H. susurratus Yasunaga & Duwal sp. nov. (Thailand); Wygomiris paveli sp. nov. (Taiwan); and W. phormictes sp. nov. (Taiwan). The male of Wygomiris nanae Yasunaga, 2012 is reported for the first time. A teratological form found on the antennae in two Wygomiris species is also documented.

Root-feeding Scarabaeidae larvae can pose a serious threat to agricultural and forest ecosystems, but many details of larval ecology are still unknown. We developed an acoustic data analysis method for gaining new insights into larval ecology. In a laboratory study, third instar larvae of Melolontha melolontha (n=38) and M. hippocastani (n=15) kept in soil-filled containers were acoustically monitored for 5 min each, resulting in the first known stridulation recordings for each species. Subsequent continuous monitoring of three M. hippocastani larvae over several hours showed that a single larva could stridulate more than 70 times per hour, and stridulation rates increased drastically with increasing larval abundance. The new fractal dimension-based data analysis method automatically detected audio sections with stridulations and provided a semi-quantitative estimate of stridulation activity. It is the first data analysis method specifically targeting Scarabaeidae larvae stridulations in soils, enabling for the first time non-invasive species-specific pest monitoring.Key messageRoot-feeding scarab beetle larvae, known as white grubs, can be serious agricultural and forest pests.White grub infestation monitoring is difficult due to their cryptic lifestyle, but detailed monitoring data is essential for effective pest control.We present the first acoustic data analysis routine targeting stridulations, using Melolontha melolontha and M. hippocastani as model organisms.This new method provides for the first time the basis for the development of tools for non-invasive, species-specific, and rapid white grub monitoring in soils.

In terms of species number, teleost fishes are the largest group of living vertebrates. Current estimates show that the majority of all known orders of teleosts include species that produce sound, many of which have clear social communication functions. Fishes exhibit a diverse range of musculoskeletal mechanisms that may have independently evolved for sound production. This includes the rapid contraction of paired vocal muscles that vibrate either the swimbladder or pectoral girdle, and the rubbing together ( stridulation) of parts of the pectoral girdle–fin complex, oral jaw, or pharyngeal teeth. By comparison, tetrapods show only two major types of vocal organs, the syrinx of birds and the larynx of all other nonavian groups. The more conserved tetrapod pattern may depend, in part, on the dependence of their vocalizations on respiration. Unlike peripheral mechanisms, the functional organization of those regions of the central nervous system (CNS) controlling vocalizations among vertebrates is highly conserved across distantly related groups of fishes and terrestrial vertebrates. Hence, the available data suggest that both vocal behaviors and the neural bases for acoustic communication first evolved among fishes and retain their basic organizational features in more recently evolved groups of tetrapods.

This chapter compiles active and passive defensive mechanisms of aquatic and semiaquatic developmental stages of all insect orders against various predators. Mainly escape reactions, mechanical defense, defensive stridulation, and especially chemical defenses are described, illustrated, and tabulated. Apart from the large aquatic groups of ephemeropteran, Odonata or Trichoptera larvae especially aquatic bugs and water beetles are considered by even including small groups from Collembola up to Mecoptera.

Acoustic signals are used for intraspecific communication in bark beetles and a variety of stridulatory mechanisms have evolved within the subfamily Scolytinae (Coleoptera: Curculionidae). Bark beetles use stridulatory signals for communication at the tree surface and within tunnels inside tree tissues. Bark beetles produce a variety of call types that are broadband with frequencies ranging from 1 to 80 kHz. Not only are airborne and substrate-borne vibrations available, but every stridulation event produces both airborne and substrate-borne vibrations via the same action of the animal. Vibrations appear to be used during species recognition, premating interactions, pair formation, mate selection, intraspecies aggression, territoriality, and predator deterrence. No sound receptors have been located for bark beetles; however, we propose potential locations in this chapter. We provide an overview of acoustic communication and its use by adult bark beetles, describe their stridulatory structures, interpret how vibrations move within tree materials and how this affects the beetles’ ecology and behavior, and present technical and applied applications of acoustic tools for bark beetle management.