Within‐Species Mate Preferences Do Not Contribute to the Maintenance of Sexually Monomorphic Mating Signals in Green Lacewings

We know much less about the evolutionary forces and constraints that maintain similar mating displays in females and males than we do about sexually dimorphic mating displays. Both female and male green lacewings have sexually monomorphic vibrational mating signals and are equally choosy against heterospecific mating signals. This similarity in between‐species sex roles may explain a large part of the presence of species‐specific female signals in these species, but does not necessarily predict why female and male signals are similar. We tested for within‐species sex‐specific similarities in mate preferences in Chrysoperla lucasina that may contribute to the maintenance of sexually monomorphic mating signals in this species. We found weak preferences and low levels of discrimination for signals with varying fine‐scale temporal features (volley duration, period, and volley‐duty cycle). The longer signals that both sexes produced in response to playback were sexually monomorphic, but some females and most males also produced shorter signals with significantly reduced volley durations and periods. Notably, all of these signals had indistinguishable volley‐duty cycles, the ratio of volley duration to volley period. We propose that mating signals in C. lucasina are maintained in both sexes because of similar between‐species mate preferences, but the sexually monomorphic mating signals cannot be attributed to significant within‐species mate preferences. What differences are present in within‐species sex roles may be resolved by a male‐biased signal polymorphism, in long and short signals that are hypothesized to have distinct functions during mate calling and courtship.     

The use of bioacoustic characters for distinguishing between cryptic species in insects: Potentials,restrictions, and prospects

Differences in acoustic signal patterns between closely related species often form the main precopulatory reproductive barrier in insects. For this reason, discrimination between similar forms based on their signal patterns allows one to recognize reproductively isolated species. A calling signal produced by a mature male for attracting a conspecific female is a “species ID” testifying to the fact that it belongs to the same species. This is the reason why the use of the calling signal analysis for discriminating between cryptic species or elucidating the taxonomic rank of dubious forms is highly efficient. In certain species, courtship signals also show species-specific patterns. In insect taxonomy, the study of acoustic signals is most promising in morphologically or/and ecologically heterogeneous groups. Chances that any morphologically homogeneous form will actually appear to be a complex of cryptic species are low. The degree of signal variability differs in different orders, families and even congeneric species. Therefore, in every taxon investigated for the first time, it is necessary to evaluate the limits of intraspecific variability of signals before using the acoustic characters in taxonomy. Species not involved in acoustic interactions due to allopatry, different host specialization, etc. can produce calling signals with identical patterns. Consequently, similarity in the signal structure in such species is by no means evidence of their synonymy.     

Female competition for availability of males in insects: the Nezara viridula (Linnaeus, 1758) model

Multimodal communication in solitary stinkbugs enables them to meet, mate and copulate. Many plant‐dwelling species exchange information during the calling phase of mating behavior using substrate‐borne vibratory signals. A female‐biased gender ratio induces rivalry and competition for a sexual partner. Female competition for males, first described among Heteroptera in three stinkbug species, revealed species specific differences and opened the question of plasticity in individually emitted temporal and frequency signal characteristics during calling and rival alternation. To address this question and gain an insight into the mechanisms underlying stinkbug female rivalry, we compared the characteristics of alternated signals in the southern green stinkbug Nezara viridula (Linnaeus, 1758) (Hemiptera: Pentatomidae). Compared to male rivalry, female rivalry is more complex, lasts longer and runs through successive phases by a combination of different song types. The male pheromone triggers alternation between females, producing song pulses that occasionally overlap each other. One female initiates the rivalry by changing individual pulses into pulse trains of three different types. The competing female alternates with pulses of changed temporal characteristics at lower levels of rivalry and by varying the frequency characteristics of pulse trains at higher levels. During female rivalry, the male either stops responding or occasionally emits calling and courtship signals in response to the female that has produced signals of steady temporal characteristics. Female rivalry shows complex and species specific patterns of information exchange at different levels with a broad‐range variation of temporal and frequency characteristics of, until now, unidentified vibratory emissions.     

Studies of vibratory signals in pentatomid bugs (Heteroptera,Asopinae) from European Russia

The vibratory signals of four species of Asopinae (Pentatomidae) from European Russia are described for the first time. The signals emitted by adult bugs are classified into three types: male rivalry signals, male calling signals, and solitary low-amplitude signals with still unknown function. The latter are similar in different species and show no species-specific features. Oscillograms and sonograms of vibratory signals are given for all the species studied.     

Vibrational playbacks and microscopy to study the signalling behaviour and female physiology of Philaenus spumarius

The meadow spittlebug Philaenus spumarius, vector of the bacterium Xylella fastidiosa, relies on vibrational communication to accomplish mating: the female calls to establish a duet with a male. A deeper knowledge of the species’ reproductive biology and behaviour would provide useful information for developing control techniques based on principles of ‘biotremology’, which studies the vibrational behaviour of animals. Playback tests were conducted on single females and male–female pairs of P. spumarius from June to October 2018, and the features of the recorded calling signals were analysed using a wavelet decomposition. Dissections were performed on females to evaluate the relationship between calling activity and ovarioles development. From August onwards, females started to emit calling signals and to develop ovarioles. Female calling activity, duration of their chirps and their responsiveness to mating increased as the season progressed, and they were correlated with ovarioles’ development and presence of mature eggs. Hence, the ovarian maturation represents a key factor in association with the development of the sexual behaviour of P. spumarius females. Conversely, males produced advertisement signals soon after adult eclosion in May, but these signals were not involved in the pair formation process. Mating was achieved only when males produced courtship signals in response to female calling signals and established with them vibrational duets starting from August. Here, we provide new information regarding the P. spumarius’ ethology and hypothesize that potential mating disruption techniques should consider the insect physiology and be applied when both sexes are responsive to mating signals.     

Sound production in Parapellopedon instabilis (Rehn, 1906) (Orthoptera: Gomphocerinae)

The sounds produced by Parapellopedon instabilis (Rehn, 1906), are described for the first time on the basis of recordings made, in captivity, with an analogical tape recorder. The signals were digitized in the laboratory and analyzed using a software. Three types of song are described: the male calling song, typical of the gomphocerinae species, the female’s agreement song, less organized temporally and unusually loud for a gomphocerinae species, and disturbance songs among males and among females, which follow the typical structure of these signals in the subfamily. Oscillograms and frequency spectra of all songs are given. The stridulatory file of both sexes, male and female, are described.     

Male orientation on vocalization perches could optimize acoustic signal transmission in anurans

Acoustic signals are distorted by vegetation, wind currents, or other sounds when transmitted through the environment. Consequently, vocalizations with features that optimize sound transmission or behaviors that improve the efficacy of communication have evolved in many animal species. Among behavioral strategies, some species call from perches above the ground to increase the propagation distance of their acoustic signals. However, the orientation in the perch also influences the transmission of the vocalizations, so that frogs calling from different orientations (i.e., horizontal, upward, or downward) may affect differently the quality and efficacy of sound transmission. We implemented a sound transmission experiment to test for the effect of calling orientation (upward, downward, and horizontal) and distance on the attenuation and degradation of advertisement calls in the common dink frog Diasporus diastema. We broadcasted and re‐recorded advertisement calls at 2 m height, setting the speaker in three directions (upward, downward, and horizontal) to simulate different signaler orientations. We found that attenuation of the advertisement calls is significantly reduced when the speaker was directed either upward or downward, rather than horizontally. However, the degradation of call is lower when the speaker is direct horizontally. Since calls produced from either upward or downward orientations could travel farther, they could be used to signal male spatial location, while calls produced from a horizontal position could provide information on male quality at shorter distances at advanced phases of courtship.     

Courtship Sounds Advertise Species Identity and Male Quality in Sympatric Pomatoschistus spp. Gobies

Acoustic signals can encode crucial information about species identity and individual quality. We recorded and compared male courtship drum sounds of the sand goby Pomatoschistus minutus and the painted goby P. pictus and examined if they can function in species recognition within sympatric populations. We also examined which acoustic features are related to male quality and the factors that affect female courtship in the sand goby, to determine whether vocalisations potentially play a role in mate assessment. Drums produced by the painted goby showed significantly higher dominant frequencies, higher sound pulse repetition rates and longer intervals between sounds than those of the sand goby. In the sand goby, male quality was predicted by visual and acoustic courtship signals. Regression analyses showed that sound amplitude was a good predictor of male length, whereas the duration of nest behaviour and active calling rate (i.e. excluding silent periods) were good predictors of male condition factor and fat reserves respectively. In addition, the level of female courtship was predicted by male nest behaviour. The results suggest that the frequency and temporal patterns of sounds can encode species identity, whereas sound amplitude and calling activity reflects male size and fat reserves. Visual courtship duration (nest-related behaviour) also seems relevant to mate choice, since it reflects male condition and is related to female courtship. Our work suggests that acoustic communication can contribute to mate choice in the sand goby group, and invites further study.     

Reproductive behaviour and vibratory communication of the neotropical predatory stink bug Podisus nigrispinus

Vibratory communication during reproductive behaviour is less well described in predatory (Asopinae) than in phytophagous (Pentatominae) stink bugs. Different steps in the mating behaviour of the predatory stink bug Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae; Asopinae) are described in the present study, together with vibratory signals emitted on artificial and natural substrate during courtship and copulation. Vibratory signals in Podisus nigrispinus have a decisive role in copulation success and are produced in both sexes by abdominal vibration and tremulation. In P. nigrispinus, one species‐specific female and two male songs, which do not show the calling function typically found in phytophagous stink bugs, are produced by abdominal vibration and are emitted during reproductive behaviour. Additionally, P. nigrispinus produces tremulatory signals that have no species or sex specificity. Tremulatory signals emitted spontaneously on a plant as a sequence of readily repeated pulses are similar to the calling songs of the Pentatominae stink bug. These signals may carry information on the presence of a mate; however, in other behavioural contexts, they may have a different function, such as advertisement or even alarm signals. Plants transmit vibratory signals produced by both mechanisms as a low‐pass filter, increasing the amount of low‐frequency components. The results of the present study raise important questions about the interaction between chemical and vibratory signals in the mating behaviour of predatory stink bugs.     

Acoustic signalling in palaeotropical bushcrickets (Orthoptera: Tettigonioidea: Pseudophyllidae): does predation pressure by eavesdropping enemies differ in the Palaeo- and Neotropics?

When producing its calling song, a male bushcricket exposes itself to predators which use this sound for localization. Male signalling therefore has to be a compromise between attracting females and avoiding predators. In this study, the calling song structure of six Malaysian bushcricket species of the family Pseudophyllidae was examined. The lowest frequency of longdistance signals in insects yet discovered is the 600 Hz produced by Tympanophyllum arcufolium. The peak frequency of all six species and three additional species, from which only handling sounds were examined, was below 12 kHz. The duty cycle (that period of time spent signalling) was low, between one and five percent in four species and more than 20 percent in the remaining two species, typical for species which rely on camouflage. None of the various types of bat avoidance behaviour observed in the neotropical Pseudophyllidae was found in the Malaysian species. This difference is discussed in regard to the possibility of different predation pressures in the Palaeo- and Neotropics.     

Geographical variation in acoustic signals of the planthopper, Nilaparvata bakeri (Muir), in Asia: species recognition and sexual selection

Populations of the planthopper .Nilaparvata bakeri (Muir) were sampled from the Philippines (Luzon), Indonesia (Bali), India (Bihar) and Sri Lanka (Central Province) from the grass Leersia hexandra (Schwartz), and cultured in Cardiff. Low intensity vibratory signals produced by males and females during mate location and courtship were recorded and analysed. Obvious differences were found between male calling songs of insects from the Philippines and those from the other three areas. Smaller differences were detected between the Indonesian, Indian and Sri Lankan populations. Hybrids between Philippine and Indonesian, and Indonesian and Sri Lankan, insects were obtained freely in the laboratory. Male calls of F, hybrids were variable and intermediate between parentals. Mate choice experiments showed no significant assortative mating between the different populations. There was no indication of reproductive isolation and therefore of different biological species. The assumption that different male calling songs necessarily indicate the presence of different biological species is not confirmed in this example.     

Calling is an honest indicator of paternal genetic quality in poison frogs

Several competing hypotheses have been put forward to explain why females of many species mate preferentially with males possessing the most conspicuous signals (e.g., ornaments, displays, or songs). We performed a laboratory experiment using two species of poison frogs, Dendrobates leucomelas and Epipedobates tricolor, to test the hypothesis that male calling performance is an honest indicator of parental quality. Our analyses are based on data from behavioral observations of mating activities of captive-reared individuals (and their offspring) that were housed in terraria for four consecutive breeding seasons. Male mating success increased with male calling rate and chirp duration in both species, suggesting that females preferred males with more elaborate calls. Because calling performance improved with age in D. leucomelas, female poison frogs that prefer males with more elaborate calls in the wild may end up mating with older males that have already proven their ability to survive. Females that mated with good callers obtained higher quality offspring. Eggs fertilized by males with high calling rates and long chirp durations had higher hatching success and produced tadpoles that were more likely to metamorphose into surviving frogs. As a consequence, females that mated with males with high calling performance obtained more surviving offspring per egg, compared to females that mated with poor callers. Collectively, our findings comply with the notion that female poison frogs prefer to mate with good callers because calling performance is a reliable predictor of offspring quality. The possible influence of maternal allocation and reasons for the strong effect size compared to previous studies are discussed.     

雄性稻绿蝽对雌性鸣唱反应的物种特异性

雌性稻绿蝽的鸣唱开始了在基质中产生的通讯并引起雄性不同的特定反应。在两种自然情况下 ,我们检验了雄性稻绿蝽对N viridula ,Thyantapallidovirens和Thyantacustatoraccerra个体鸣唱刺激反应的物种特异性水平 ,并对反应强度和同种及异种刺激性鸣唱的时间特性进行了相关分析 ,证明雄性求偶鸣唱的发送和震动源的定位是最具物种特异性的反应。然而 ,即便是在这个水平上 ,雄性稻绿蝽不能将同种雌性个体的鸣唱与T .custatoraccera的第二个雄性个体的鸣唱区分开来 ,后者与前者有相似的脉冲持续时间和重复时间值。本文也讨论了涉及交配行为鸣唱期的有关信号的物种特定性的概念     

The influence of age and size on temporal mate signalling behaviour

I investigated how male size, condition and age influence both time spent calling and how signals are apportioned throughout the night (i.e. temporal calling pattern) in the Texas field cricket, Gryllus integer. I quantified male calling time and temporal calling pattern using an electronic apparatus that continuously monitored male calling/noncalling behaviour throughout the night. Male condition, measured using the residuals from an allometric regression of male mass on overall body size, did not explain any variation in either time spent calling or temporal calling pattern. However, some intrapopulation variation in time spent calling and temporal calling pattern was explained by differences in male size and age. Large males called more often than small males. Young and very old adult males called significantly less often than middle-age males. As males aged they initiated calling earlier in the evening, probably increasing their susceptibility to parasitism by the tachinid parasitoid Ormia ochracea. Overall, age and size differences explained 10-40% of signalling variation in male G. integer. Copyright 2000 The Association for the Study of Animal Behaviour.     

The Sounds of Silence as an Alarm Cue in Túngara Frogs,Physalaemus pustulosus

In many species males vocally advertise for mates in choruses and these choruses serve as acoustic beacons to conspecific females as well as to eavesdropping predators and parasites. Chorusing will often cease in response to disturbances, such as the presence of predators. In some cases the cessation is so rapid and over such a large area that it seems improbable that males are all responding directly to the same local disturbance. Here, we demonstrate experimentally in Neotropical túngara frogs, Physalaemus pustulosus, that the cessation of calling by males spreads rapidly through the chorus. The cessation of chorusing in response to the cessation of playbacks of three calling males is more effective in inducing chorus cessation than is the cessation of one male calling. When three males are calling, the cessation of complex calls is more effective in inducing chorus cessation than simple calls. There is no main effect on whether the final call of the male is complete or is interrupted. We thus conclude that the sudden lack of signals—the ‘sounds of silence’—becomes an alarm cue that can explain the rapid cessation of choruses that are common in many chorusing species.     

Vocal communication in frogs

The robust nature of vocal communication in frogs has long attracted the attention of natural philosophers and their biologically inclined successors. Each frog species produces distinctive calls that facilitate pre-mating reproductive isolation and thus speciation. In many terrestrial species, a chorus of simultaneously calling males attracts females to breeding sites; reproductive females then choose and locate one male, using distinctive acoustic cues. Males compete with each other vocally and sometimes physically as well. Anuran acoustic signaling systems are thus subject to the strong pressures of sexual selection. We are beginning to understand the ways in which vocal signals are produced and decoded by the nervous system and the roles of neurally active hormones in both processes.     

Signal diversification in Oecanthus tree crickets is shaped by energetic,morphometric, and acoustic trade‐offs

Physiology, physics, and ecological interactions can generate trade‐offs within species, but may also shape divergence among species. We tested whether signal divergence in Oecanthus tree crickets is shaped by acoustic, energetic, and behavioral trade‐offs. We found that species with faster pulse rates, produced by opening and closing wings up to twice as many times per second, did not have higher metabolic costs of calling. The relatively constant energetic cost across species is explained by trade‐offs between the duration and repetition rate of acoustic signals—species with fewer stridulatory teeth closed their wings more frequently such that the number of teeth struck per second of calling and the resulting duty cycle were relatively constant across species. Further trade‐offs were evident in relationships between signals and body size. Calling was relatively inexpensive for small males, permitting them to call for much of the night, but at low amplitude. Large males produced much louder calls, reaching up to four times more area, but the energetic costs increased substantially with increasing size and the time spent calling dropped to only 20% of the night. These trade‐offs indicate that the trait combinations that arise in these species represent a limited subset of conceivable trait combinations.     

The Influence of Substrate on Male Responsiveness to the Female Calling Song in Nezara viridula

The female calling song (FCS) of the southern green stink bug Nezara viridula is composed of vibrational pulse trains that include either short pulses and a long pulse (FCS-1) or just short pulses (FCS-2). Their function in communication was studied by investigating male vibratory responses to natural and artificial signals on artificial and natural substrates. On a loudspeaker membrane, FCS-1 triggered in males from a Slovene and a French population significantly more courtship songs (MCrS) than FCS-2. Experiments with artificial signals showed that male responses are modulated by the duration of pulse trains and pulse repetition time. On a bean plant, males of both populations responded in the same way to the two types of female calling song pulse trains. Moreover, a laser vibrometer study of the transmission of different natural and artificial vibratory signals through the bean plant showed that the pulses of a high repetition rate are prolonged and fused at distances from the emitter. We conclude that female calling song pulse trains of different temporal structure have the same function in vibrational communication of the species. The temporal and spectral structures of the female calling songs of N. viridula are discussed in terms of effective transmission through plants.     

Songs of Holcostethus strictus (Fabricius): a different repertoire among landbugs (Heteroptera: Pentatomidae)

Songs emitted during mating by male and female Holcostethus strictus were recorded as substrate vibrations. Spectra of the vibrational signals have a dominant frequency peak between 100 and 260 Hz and in this respect reflect the general characteristic of the family Pentatomidae. Songs of H. strictus differ from the song repertoire of the southern green stink bug Nezara viridula (L.) (Pentatomidae) in many respects. The female calling and courtship songs differ in echeme and phrase duration. The male calling song is composed of spectrally different subunits. The male courtship song is characterised by three types of spectrally and temporally different echemes. The male copulatory song is composed of echemes of two types, which constitute a phrase of less regular temporal structure. In H. strictus, males start to sing first and female songs are less complex than in N. viridula. The female calling song is evoked by male calling and does not trigger male response. The female and male courtship song phrases are superimposed on one another and we have not observed any obvious regularity in their exchange. The possible role of different songs in H. strictus is discussed and compared with that in other pentatomide landbug species.