Time and habitat structure shape insect acoustic activity in the Amazon.

Insects are the most diverse animal taxon on Earth and play a key role in ecosystem functioning. However, they are often neglected by ecological surveys owing to the difficulties involved in monitoring this small and hyper-diverse taxon. With technological advances in biomonitoring and analytical methods, these shortcomings may finally be addressed. Here, we performed passive acoustic monitoring at 141 sites (eight habitats) to investigate insect acoustic activity in the Viruá National Park, Brazil. We first describe the frequency range occupied by three soniferous insect groups (cicadas, crickets and katydids) to calculate the acoustic evenness index (AEI). Then, we assess how AEI varies spatially and temporally among habitat types, and finally we investigate the relationship between vegetation structure variables and AEI for each insect category. Overall, crickets occupied lower and narrower frequency bands than cicadas and katydids. AEI values varied among insect categories and across space and time. The highest acoustic activity occurred before sunrise and the lowest acoustic activity was recorded in pastures. Canopy cover was positively associated with cricket acoustic activity but not with katydids. Our findings contribute to a better understanding of the role of time, habitat and vegetation structure in shaping insect activity within diverse Amazonian ecosystems. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Satellite remote sensing of environmental variables can predict acoustic activity of an orthopteran assemblage.

Passive acoustic monitoring (PAM) is a promising method for biodiversity assessment, which allows for longer and less intrusive sampling when compared to traditional methods (e.g., collecting specimens), by using sound recordings as the primary data source. Insects have great potential as models for the study and monitoring of acoustic assemblages due to their sensitivity to environmental changes. Nevertheless, ecoacoustic studies focused on insects are still scarce when compared to more charismatic groups. Insects' acoustic activity patterns respond to environmental factors, like temperature, moonlight, and precipitation, but community acoustic perspectives have been barely explored. Here, we provide an example of the usefulness of PAM to track temporal patterns of acoustic activity for a nocturnal assemblage of insects (Orthoptera). We integrate satellite remote sensing and astronomically measured environmental factors at a local scale in an Andean Forest of Colombia and evaluate the acoustic response of orthopterans through automated model detections of their songs for nine weeks (March and April of 2020). We describe the acoustic frequency range and diel period for the calling song of each representative species. Three species overlapped in frequency and diel acoustics but inhabit different strata: canopy, understory, and ground surface level. Based on the acoustic frequency and activity, we identified three trends: (i) both sampled cricket species call at lower frequency for shorter periods of time (dusk); (ii) all sampled katydid species call at higher frequency for longer time periods, including later hours at night; and (iii) the diel acoustic activity span window seems to increase proportionally with dominant acoustic frequency, but further research is required. We also identified a dusk chorus in which all the species sing at the same time. To quantify the acoustic response to environmental factors, we calculated a beta regression with the singing activity as a response variable and moon phase, surface temperature and daily precipitation as explanatory variables. The response to the moon phase was significant for the katydids but not for the crickets, possibly due to differences in diel activity periods. Crickets are active during dusk, thus the effects of moonlight on acoustic activity are negligible. The response to precipitation was significant for the two crickets and not for the katydids, possibly because of higher likelihood of rain interrupting crickets' shorter diel activity period. Our study shows how the local survey of orthopteran acoustic assemblages, with a species taxonomic resolution coupled with remote-sensing environmental measurements can reveal responses to environmental factors. In addition, we demonstrate how satellite data might prove to be a useful alternative source of environmental data for community studies with geographical, financial, or other constraints.

Acoustic and vibrational signaling in true katydid Nesoecia nigrispina: three means of sound production in one species.

The males of Mexican katydids Nesoecia nigrispina (Stal, 1873) produce calling songs and protest sounds using the typical stridulatory apparatus, situated, as in most of the other Ensifera, at the bases of the tegmina. It includes a stridulatory file on the upper tegmen and a plectrum on the lower one. The calling sounds, which are of two types (fast and slow), are two-syllabic series, with a repetition rate fluctuate within 3-4.5 s-1 (fast) and 1.2-2 s-1 (slow). After tactile stimulation, males produce protest signals in the form of short trills of uniform syllable duration. The syllable repetition rate is higher than that of the calling sounds: 7.7 s-1. The frequency spectra of these signals have maxima in the band of 14-15 kHz. However, in addition to the sounds described, both males and females are capable of producing protest signals of the second type, with the help of another sound apparatus, namely the hind wings. Apparently, the sound is produced by the friction of the hind wings on the lower tegmen. The dominant frequencies in the frequency spectra of these sounds are 40-60 kHz. In adults of both sexes and older nymphs, in response mainly to tactile stimulation, short clicks are recorded, which they produce, apparently, by the mandibles. Thus, N. nigrispina seems to have the most extensive acoustic repertoire among pseudophyllines and three means of emitting sound signals. Tremulatory substrate-borne vibrations are produced by individuals of both sexes during courtship and by males completing the calling signal cycle and after copulation. It is possible that vibrational signals are an additional factor in the reproductive isolation of sympatric species, since the calling sound signals in representatives of the genus Nesoecia are similar and exhibit considerable variability. The type and parameters of the calling signal used by the female during recognizing a conspecific mate remain unclear.

Are all auditory sensilla of bushcrickets bimodal? Comment on: R. D. Zhantiev and O. S. Korsunovskaya, Functions of chordotonal sensilla in bushcrickets (Orthoptera, Tettigoniidae); Entomological Review, 2021, vol. 101 (6), pp. 755-766.

Detection of sound and substrate vibration is crucial for the survival and reproduction of many animals, particularly insects. Bushcrickets (Orthoptera, Tettigoniidae), developed a large mechanosensory organ complex in their legs to detect such stimuli. As demonstrated by various studies in the past, sensilla in distinct functional groups form specialized vibratory organs (the subgenual organ and the accessory organ), respond sensitively to both vibration and sound (in the intermediate organ [IO]), or mediate hearing (in the crista acustica [CA]; the tympanal hearing organ). In their recent publication, Zhantiev and Korsunovskaya addressed auditory and vibratory sensitivity in the IO and the CA in two species of bushcrickets, using single-cell recording and staining of sensory neurons from their soma in an isolated foreleg. Their main finding was that not only the IO but also the complete CA contains bimodal sensilla responding with high sensitivity to both sound and vibration, which would be a true change in the paradigm of how the auditory/vibratory sense in Orthoptera works. In addition, they revealed vibratory tuning of the IO sensilla, which differs largely from that in previous studies. We propose three major experimental causes of such discrepancies: calibration, experiments with isolated legs, and differences in the sites of recording. To judge the causes of these discrepancies more adequately, a detailed comparison of methods and a number of control experiments are needed. This will deepen our understanding of sensory adaptations and specialization of insect mechanosensory organs to stimuli entering the system by different input pathways.

Ovipositor and mouthparts in a fossil insect support a novel ecological role for early orthopterans in 300 million years old forests.

A high portion of the earliest known insect fauna is composed of the so-called 'lobeattid insects', whose systematic affinities and role as foliage feeders remain debated. We investigated hundreds of samples of a new lobeattid species from the Xiaheyan locality using a combination of photographic techniques, including reflectance transforming imaging, geometric morphometrics, and biomechanics to document its morphology, and infer its phylogenetic position and ecological role. Ctenoptilus frequens sp. nov. possessed a sword-shaped ovipositor with valves interlocked by two ball-and-socket mechanisms, lacked jumping hind-legs, and certain wing venation features. This combination of characters unambiguously supports lobeattids as stem relatives of all living Orthoptera (crickets, grasshoppers, katydids). Given the herein presented and other remains, it follows that this group experienced an early diversification and, additionally, occurred in high individual numbers. The ovipositor shape indicates that ground was the preferred substrate for eggs. Visible mouthparts made it possible to assess the efficiency of the mandibular food uptake system in comparison to a wide array of extant species. The new species was likely omnivorous which explains the paucity of external damage on contemporaneous plant foliage.

Daily Signaling Rate and the Duration of Sound per Signal are Negatively Related in Neotropical Forest Katydids.

Researchers have long examined the structure of animal advertisement signals, but comparatively little is known about how often these signals are repeated and what factors predict variation in signaling rate across species. Here, we focus on acoustic advertisement signals to test the hypothesis that calling males experience a tradeoff between investment in the duration or complexity of individual calls and investment in signaling over long time periods. This hypothesis predicts that the number of signals that a male produces per 24 h will negatively correlate with (1) the duration of sound that is produced in each call (the sum of all pulses) and (2) the number of sound pulses per call. To test this hypothesis, we measured call parameters and the number of calls produced per 24 h in 16 species of sympatric phaneropterine katydids from the Panamanian rainforest. This assemblage also provided us with the opportunity to test a second taxonomically specific hypothesis about signaling rates in taxa such as phaneropterine katydids that transition from advertisement calls to mating duets to facilitate mate localization. To establish duets, male phaneropterine katydids call and females produce a short acoustic reply. These duets facilitate searching by males, females, or both sexes, depending on the species. We test the hypothesis that males invest either in calling or in searching for females. This hypothesis predicts a negative relationship between how often males signal over 24 h and how much males move across the landscape relative to females. For the first hypothesis, there was a strong negative relationship between the number of signals and the duration of sound that is produced in each signal, but we find no relationship between the number of signals produced per 24 h and the number of pulses per signal. This result suggests the presence of cross-taxa tradeoffs that limit signal production and duration, but not the structure of individual signals. These tradeoffs could be driven by energetic limitations, predation pressure, signal efficacy, or other signaling costs. For the second hypothesis, we find a negative relationship between the number of signals produced per day and proportion of the light trap catch that is male, likely reflecting males investing either in calling or in searching. These cross-taxa relationships point to the presence of pervasive trade-offs that fundamentally shape the spatial and temporal dynamics of communication.

Songs in the genus Uromenus (Orthoptera: Tettigoniidae: Ephippigerini): A review with new information about some species.

With nearly 60 described forms Uromenus is the most species-rich genus of the tribe Ephippigerini, a west Palearctic group of flightless bush-crickets (katydids). As it is typical for bush-crickets, Uromenus males produce species-specific calling songs to attract females prepared to mate. These insects are relatively large and their songs have always components audible to humans. Nevertheless, acoustical information are available only for few species. Also the phylogenetic relationships of species and species groups are poorly known. In this paper we present new data on the song and morphology of several species (U. dyrrhachiacus, U. elegans, U. finoti, U. galvagnii, U. robustus, U. tobboganensis and U. innocentii) and give a review of all published acoustical data. Judging from the still few data, as in other Ephippigerini the song patterns often seem to contain species-group characteristics making them candidates to be used in phylogenetic studies. Additionally, we have studied the female stridulatory organs which are unique in structure in Ephippigerini and completely different from those of the males. Despite in Uromenus used only for defensive stridulation, possibly species-specific similarities in structure between males and females exist.

Redescription of emRaggophyllum/em Nickle, 1967 (Orthoptera: Tettigoniidae: Phaneropterinae) with description of a new species from Brazilian Amazon Rainforest and placement in Microcentrini Brunner von Wattenwyl, 1878.

Raggophyllum Nickle, 1967 is a monotypic genus, including Raggophylluym spinosum, and recorded in Peru and Bolivia. In this work, Raggophyllum is redescribed and assigned to the Microcentrini, based on the type species Raggophylluym spinosum. Raggophyllum rubrofemoratum sp. nov. in described from Brazil, Acre and Amazonas, and it is the first record for the genus in Brazil. The male genitalia and the stridulatory file morphology are described for the first time. A distribution map, notes on the habitat, and commentaries on their distribution among Amazonian endemism areas are included.

Material heterogeneity of male genitalia reduces genital damage in a bushcricket during sperm removal behaviour.

Sperm removal behaviour (SRB) is known in many animals, and male genital structures are often involved in the SRB, e.g. rubbing female genitalia vigorously. However, it remains unclear how those male genital structures function properly without severe genital damage during SRB. In the present study, we focused on the bushcricket Metaplastes ornatus and examined the biomechanics of male and female genital structures, involved in their SRB as a model case. During an initial phase of mating, males of this species thrust their subgenital plate with hook-like spurs and many microscopic spines into the female genital chamber. By moving the subgenital plate back-and-forth, males stimulate females, and this stimulation induces the ejection of sperm previously stored in females. We aimed to uncover the mechanics of the interaction between the subgenital plate and genital chamber during SRB. The genital morphology and its material composition were investigated using modern imaging and microscopy techniques. The obtained results showed a pronounced material heterogeneity in the subgenital plate and the genital chamber. The material heterogeneity was completely absent in that of a second bushcricket species, Poecilimon veluchianus, which does not exhibit SRB. Finite element simulations showed that the specific material heterogeneity can redistribute the stress in the subgenital plate of M. ornatus and, thereby, reduces stress concentration during SRB. This may explain why only a few examined males had a broken spur. We suggest that the observed structural features and material heterogeneity in M. ornatus are adaptations to their SRB.

On the tympanic membrane impedance of the katydid Copiphora gorgonensis (Insecta: Orthoptera: Tettigoniidae).

Katydids (bush-crickets) are endowed with tympanal ears located in their forelegs' tibiae. The tympana are backed by an air-filled tube, the acoustic trachea, which transfers the sound stimulus from a spiracular opening on the thorax to the internal side of the tympanic membranes (TM). In katydids the sound stimulus reaches both the external and internal side of the membranes, and the tympanal vibrations are then transferred to the hearing organ crista acustica (CA) that contains the fluid-immersed mechanoreceptors. Hence the tympana are principally involved in transmitting and converting airborne sound into fluid vibrations that stimulate the auditory sensilla. Consequently, what is the transmission power to the CA? Are the TM tuned to a certain frequency? To investigate this, the surface normal acoustic impedance of the TM is calculated using finite-element analysis in the katydid Copiphora gorgonensis. From this, the reflectance and transmittance are obtained at the TM. Based on the impedance results obtained from the pressure recordings at TM and the velocity field calculations in the AT, in the frequency range 5-40 kHz, it is concluded that the tympana have considerably higher transmission around 23 kHz, corresponding to the dominant frequency of the male pure-tone calling song in this species.

Demonstrating sexual selection by cryptic female choice on male genitalia: What is enough?

Rapid divergence in external genital structures occurs in nearly all animal groups that practice internal insemination; explaining this pattern is a major challenge in evolutionary biology. The hypothesis that species-specific differences in male genitalia evolved under sexual selection as courtship devices to influence cryptic female choice (CFC) has been slow to be accepted. Doubts may stem from its radical departure from previous ideas, observational difficulties because crucial events occur hidden within the female's body, and alternative hypotheses involving biologically important phenomena such as speciation, sperm competition, and male-female conflicts of interest. We assess the current status of the CFC hypothesis by reviewing data from two groups in which crucial predictions have been especially well-tested, Glossina tsetse flies and Roeseliana (formerly Metrioptera) roeselii bushcrickets. Eighteen CFC predictions have been confirmed in Glossina and 19 in Roeseliana. We found data justifying rejection of alternative hypotheses, but none that contradicted CFC predictions. The number and extent of tests confirming predictions of the CFC hypothesis in these species is greater than that for other generally accepted hypotheses regarding the functions of nongenital structures. By this criterion, it is reasonable to conclude that some genital structures in both groups likely involved sexual selection by CFC.

Complex wing motion during stridulation in the katydid Nastonotus foreli (Orthoptera: Tettigoniidae: Pseudophyllinae).

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 tooth-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 frequency) 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, relatively narrowband calls at ≈20 kHz. 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.

Innate releasing mechanisms and fixed action patterns: basic ethological concepts as drivers for neuroethological studies on acoustic communication in Orthoptera.

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.

Phylogeny and acoustic signal evolution of a pure tone song katydid Pseudophyllus titan (Orthoptera: Tettigoniidae) based on the complete mitogenome.

Ensifera is an extremely diverse group in the order Orthoptera, and it has been the subject of considerable research, especially in terms of phylogeny and bioacoustics. Katydids are known for using high-frequency broadband signals whereas most cricket songs are pure tones with a frequency range of 2-8 kHz. Pseudophyllus titan is a special katydid emits low-frequency pure tone songs similar to that of crickets. Acoustic communication of Ensifera were widely studied, but song evolution could deserve new examination taking into account the newly available phylogenies. To examine the song evolution of P. titan in the Ensifera, the mitogenomes of P. titan and three other ensiferan species (Sphagniana ussuriana, Oecanthus sinensis, Truljalia hibinonis) were obtained by high-throughput sequencing. In addition, the phylogeny of Ensifera was reconstructed including 63 in-group taxa, and the divergence time was further estimated for major ensiferan lineages. Lastly, the evolutions of song frequency were evaluated based on an ancestral character state reconstruction (ACSR). Moreover, we have studied the calling songs of 78 katydids and performed ACSR based on five genes. All phylogeny analyses confirmed that the superfamily Schizodactyloidea was placed basally to the non-grylloid clade. P. titan was in the Pseudophyllinae clade, and this clade had a distant relationship form other lineages in Phaneropteridae. The ACSR showed that P. titan evolved low-frequency pure tone songs independently after ancestors of katydids evolved high-frequency broadband noise. Referring to the geologic time scale, we suggest that the song frequency evolution in the Ensifera to some extent caused by adaptations to the changing habitat under conditions of climate change and plant evolution.

Information use during movement regulates how fragmentation and loss of habitat affect body size.

An individual's body size is central to its behaviour and physiology, and tightly linked to its movement ability. The spatial arrangement of resources and a consumer's capacity to locate them are therefore expected to exert strong selection on consumer body size. We investigated the evolutionary impact of both the fragmentation and loss of habitat on consumer body size and its feedback effects on resource distribution, under varying levels of information used during habitat choice. We developed a mechanistic, individual-based, spatially explicit model, including several allometric rules for key consumer traits. Our model reveals that as resources become more fragmented and scarce, informed habitat choice selects for larger body sizes while random habitat choice promotes small sizes. Information use may thus be an overlooked explanation for the observed variation in body size responses to habitat fragmentation. Moreover, we find that resources can accumulate and aggregate if information about resource abundance is incomplete. Informed movement results in stable resource-consumer dynamics and controlled resources across space. However, habitat loss and fragmentation destabilize local dynamics and disturb resource suppression by the consumer. Considering information use during movement is thus critical to understand the eco-evolutionary dynamics underlying the functioning and structuring of consumer communities.

Female perception of copulatory courtship by male titillators in a bushcricket.

Males of the bushcricket Metrioptera roeselii bear paired titillators that are spiny genital structures supposedly functioning as copulatory courtship devices. During copulation, the male inserts its titillators into the female's genital chamber, where they rhythmically tap on the sensilla-covered dorsal surface of the genital fold. Here, we investigated the stimulatory function of male titillators during mating in M. roeselii Tracer backfills of presumptive mechanosensory sensilla at the female genital fold revealed a thick bundle of sensory axons entering the last unfused abdominal ganglion (AG-7). Electrophysiological recordings of abdominal nerves demonstrated that females sense mechanical stimulation at their genital fold. The mechanosensory responses, however, were largely reduced by the insecticide pymetrozine that selectively blocks scolopidia of internal chordotonal organs but not campaniform and hair sensilla on the outer cuticle surface. In mating experiments, the females showed resistance behaviours towards males with asymmetrically shortened titillators, but the resistance was largely reduced when mechanoreceptors at the female's genital fold were either pharmacologically silenced by pymetrozine or mechanically blocked by capping with UV-hardened glue. Our findings support the hypothesis that the male titillators in these bushcrickets may serve as copulatory courtship devices to mechanically stimulate the female genitalia to reduce resistance behaviour.

Ultrastructure and electrophysiology of thermosensitive sensilla coeloconica in a tropical katydid of the genus Mecopoda (Orthoptera, Tettigoniidae).

In many acoustic insects, mate finding and mate choice are primarily based on acoustic signals. In several species with high-intensity calling songs, such as the studied katydid Mecopoda sp., males exhibit an increase in their thoracic temperature during singing, which is linearly correlated with the amount of energy invested in song production. If this increased body temperature is used by females as an additional cue to assess the male's quality during mate choice, as has been recently hypothesized ("hot-male" hypothesis), thermosensory structures would be required to evaluate this cue. In the present study, therefore, we investigated the ultrastructure and physiology of thermosensitive sensilla coeloconica on the antennal flagella of Mecopoda sp. using a combination of electron microscopy and electrophysiological recording techniques. We could identify three distinct types of sensilla coeloconica based on differences in the number and branching pattern of their dendrites. Physiological recordings revealed the innervation by antagonistically responding thermoreceptors (cold and warm) and bimodal hygro-/thermoreceptors (moist or dry) in various combinations. Our findings indicate that Mecopoda sp. females are capable of detecting a singing male from distances of at least several centimetres solely by assessing thermal cues.

Consistent Between-Individual Differences in Foraging Performance in a Floriphilic Katydid in Response to Different Choices.

The neural constraint hypothesis is one of the central ideas for the understanding of insect-plant interaction but there are still knowledge gaps in the data for foraging behavior and the performance of herbivores, and particularly florivores. We used a floriphilic katydid, Phaneroptera brevis (Serville, 1838) (Orthoptera: Tettigoniidae) and a naturalized weed, Bidens pilosa L. (Asteraceae) in caged experiments in an insectary to answer these questions: 1) How does the foraging performance of the floriphilic katydid vary when exposed to a choice in the number of capitula and types of florets of B. pilosa? 2) Does the foraging performance of the katydid, when exposed to multiple choices, improve with time, and are between-individual differences in foraging performance consistent? We observed that having more choices in the floret types and number of capitula is generally associated with a reduced foraging performance of the katydids. Floret types and number of capitula, however, did not have an interactive effect on foraging performance. We also found that the differences in foraging performance in response to choice tend to be consistent between katydids but each katydid became more efficient and decisive over time. That learning and experience can improve the foraging performance of the katydid has provided us with some insights as to how a continuum of efficient and inefficient katydids can be maintained in a population.

Exaggerated male legs increase mating success by reducing disturbance to females in the cave weta Pachyrhamma waitomoensis.

Mate guarding is a widespread behaviour resulting from sperm competition and conflict over optimal remating rates. It is a key way in which males exhibit differential mating investment, and represents a complex interplay between mating effort, intrasexual competition, opportunity costs and sexual conflict. Nevertheless, although there are many examples of exaggerated male structures used to fight rivals, few animals have developed specialized male morphological adaptations for directly sheltering females from disturbance by non-rivals. Here we report on the use of sexually dimorphic, elongated male hind legs, which are used to guard females in the New Zealand cave weta Pachyrhamma waitomoensis (Orthoptera: Rhaphidophoridae). We found that male hind legs alongside the female failed to deter rivals from accessing her or disrupting copulation. However, they did reduce the disturbance to females from other, non-rival animals such as juveniles and heterospecifics. Males with longer hind legs were more effective in reducing disturbance, and remained with females for longer. Longer guarding periods also led to higher numbers of matings between pairs. Models of males with artificially altered hind leg dimensions also showed a benefit to greater leg length, and artificially altering the disturbance rate to females also had a significant effect on pair duration. Our results indicate that nuisance disturbance to females may play an important role in driving sexual selection on male leg length and its exaggeration in this species.

Landscape Effects on Reproduction of Euschistus servus (Hemiptera: Pentatomidae), a Mobile, Polyphagous, Multivoltine Arthropod Herbivore.

Landscape factors can significantly influence arthropod populations. The economically important brown stink bug, Euschistus servus (Say) (Hemiptera: Pentatomidae), is a native mobile, polyphagous and multivoltine pest of many crops in southeastern United States and understanding the relative influence of local and landscape factors on their reproduction may facilitate population management. Finite rate of population increase (λ) was estimated in four major crop hosts-maize, peanut, cotton, and soybean-over 3 yr in 16 landscapes of southern Georgia. A geographic information system (GIS) was used to characterize the surrounding landscape structure. LASSO regression was used to identify the subset of local and landscape characteristics and predator densities that account for variation in λ. The percentage area of maize, peanut and woodland and pasture in the landscape and the connectivity of cropland had no influence on E. servus λ. The best model for explaining variation in λ included only four predictor variables: whether or not the sampled field was a soybean field, mean natural enemy density in the field, percentage area of cotton in the landscape and the percentage area of soybean in the landscape. Soybean was the single most important variable for determining E. servus λ, with much greater reproduction in soybean fields than in other crop species. Penalized regression and post-selection inference provide conservative estimates of the landscape-scale determinants of E. servus reproduction and indicate that a relatively simple set of in-field and landscape variables influences reproduction in this species.