Biology of <Emphasis Type="Italic">Tetrix bolivari</Emphasis> (Orthoptera: Tetrigidae)

The ecological requirements and biology of the Tetrigidae are almost unknown. The aim of the present work is to contribute to the knowledge of Tetrix bolivari, one of the least studied species of European Tetrigidae, by investigating its seasonal and daily activity, food biology, and vibratory communication. Adults of T. bolivari were found from March to September, with the greatest number of detections occurring between May and August. Based on the study of the daily activity patterns, most activities were positively correlated with temperature and negatively correlated with relative humidity. Detritus and mosses were the main components of the diet, with the most frequently consumed mosses being Bryum caespiticium and Bryum argenteum. Substrate-borne vibrational signals used in communication of T. bolivari are described here in detail for the first time. We distinguished four structural types of vibrational signals produced by males, including the signal produced by wing tremulation.     

Visual Communication Behaviour as a Mechanism Behind Reproductive Interference in Three Pygmy Grasshoppers (Genus Tetrix, Tetrigidae, Orthoptera)

Specific mate recognition systems should enable species to recognize conspecific mates correctly. However, heterospecific matings have been observed in a variety of taxa. One of these cases is the pygmy grasshopper genus Tetrix, in which three species show sexual interactions. T. ceperoi males mount preferably females of T. subulata, but they are rejected as mates. T. subulata males prefer T. undulata females over conspecific females and heterospecific matings occur. Here, we study the underlying behavioural mechanisms of this pattern by analysing the visual courtship behaviour of the three species videographically. We test the hypothesis that the displays of T. ceperoi are highly differentiated from the other species, while the courtship of T. subulata and T. undulata is more similar. This is supported by our results: while T. ceperoi males perform a fast movement of high amplitude (“pronotal bobbing”), the other two species show only minor movements (“lateral swinging,” “frontal swinging”). The first function of a discriminant analysis of the temporal dimensions of the displays explained 96% of the variance. 100% of the T. ceperoi displays were classified correctly, whereas only 50% of the T. subulata and 81% of the T. undulata displays were grouped accurately. A two-way ANOVA revealed no significant effects of the direction of the “swinging” movements (laterally or frontally) and no interactions between direction and species either, whereas each temporal parameter differed significantly between the three species. The highest degree of differentiation was found between T. ceperoi and T. undulata, while T. subulata and T. undulata only differed significantly in two of the six temporal parameters. Our results suggest that the mismatings between T. undulata and T. subulata are caused by an insufficient specificity of the courtship behaviour. Apparently, ecological segregation of these two species could impede sexual interactions in the field.     

Mate searching in Ennya maculicornis (Membracidae: Polyglyptini) initiated by females: behavioural and acoustic descriptions

1. In treehoppers in which courtship has been studied, males initiate the search for females by periodically emitting a vibrational signal. The responses by the female are used by males as a beacon and give rise to a duet. 2. Courtship and mating of the treehopper Ennya maculicornis were characterised through the simultaneous recording of vibrational signals and the behaviour of males and females in an arena. 3. In E. maculicornis, female initiated mate searching. Females produced two types of signals during the this process: (i) a signal that preceded the approach by the male and (ii) a signal that preceded mating. Males emitted two signals associated with two stereotyped body movements: (i) a signal produced as a response to the first signal emitted by the female, involving a change in the male's locomotory mode and the approach to the female, and (ii) a signal produced after finding and holding on to the female, involving simultaneous abdomen raising and wing fluttering. These signals were repeated several times before the female emitted the second signal. The four signalling patterns were observed in all recordings in which mating was observed. When any of the signals was missing, mating did not occur. 4. Female‐biased sex ratios in E. maculicornis, along with iteroparity, are suggested to explain the initiation of mate searching behaviour by females. A comparison of data with that from other treehoppers indicates that vibrational signals and their associated behaviour are more diverse among treehoppers than has been appreciated previously.     

Reproductive interference in two ground-hopper species: testing hypotheses of coexistence in the field

Similar to resource competition, reproductive interference may hamper the coexistence of closely related species. Species that utilize similar signal channels during mate finding may face substantial fitness costs when they come into contact and demographic displacement of the inferior species (sexual exclusion) is a likely outcome of such interactions. The two ground‐hopper species Tetrix ceperoi and Tetrix subulata broadly overlap in their ranges and general habitat requirements, but rarely co‐occur on a local scale. Results from laboratory and field experiments suggest that this mosaic pattern of sympatry might be influenced by reproductive interference. Here, we examine the significance of sexual interactions for these species in the field and test hypotheses on mechanisms of coexistence. Our results show that heterospecific sexual interactions also occur under field conditions, but in contrast to the experiments T. ceperoi was not the inferior species. The number of male mating attempts of both species was strongly correlated with encounter frequencies. Males discriminated between the sexes but not between the species, suggesting an incomplete mate recognition system in both species. The analysis of microhabitat preferences and spatial distribution revealed that habitat partitioning is not a suitable mechanism of coexistence in this system. Instead, the costs of reproductive interference are substantially mitigated by different niche breadths leading to different degrees of aggregation. Despite a considerable niche overlap T. ceperoi displayed a stronger preference for bare ground and occurred more aggregated than T. subulata, which had a broader niche. These differences may reduce the frequencies of heterospecific encounters and interactions in the field. Our results demonstrate that coexistence in the presence of reproductive interference is comparable to resource competition, being strongly influenced by ecological traits of the involved species, such as niche breadth and dispersion pattern.     

Courtship and spawning sounds in bird wrasse Gomphosus varius and saddle wrasse Thalassoma duperrey

Acoustic signals from the bird wrasse Gomphosus varius and saddle wrasse Thalassoma duperrey were recorded on coral reefs in Hawaii. Terminal phase males in both species emit two types of pulse trains (type I and type II). Type I pulses were produced during spawning and courtship, while type II pulses were associated only with courtship behaviours. Gomphosus varius type I pulses were of lower frequency than T. duperrey type I pulses (271 v. 840 Hz) and were of narrower band. Discriminant function analyses revealed interspecific differences between type I pulse trains and individual pulses of both types. This study is the first documentation of courtship and spawning sounds in sympatric labrids and shows divergence in acoustic signals.     

Habitat preferences of an endangered insect species,Cepero’s ground-hopper (<Emphasis Type="Italic">Tetrix ceperoi</Emphasis>)

Preventing the global decline in biodiversity is a major task for conservation biologists. Although habitat loss has been identified as a key factor driving extinction processes, our knowledge on the habitat requirements of many endangered species, particularly invertebrates, is still sparse. We present a feasible method to study the microhabitat preferences of insect species. In Central Europe, the endangered Cepero’s ground-hopper, Tetrix ceperoi, is believed to have its only remaining natural habitats in dune slacks of the Wadden Sea Islands. Our results suggest that this species performs an active habitat choice of damp, bare patches with high temperatures. While ponds and fens in dune slacks provide large areas of damp bare ground and algal mats, grasslands, degraded dune slacks and the transitional zone between salt marsh and dunes are less suited as habitats. The major threat for T. ceperoi is found in the succession of its pioneer habitats due to the reduced natural dynamics. In industrialized countries, pioneer habitats and species are threatened substantially by coastal protection and floodplain regulation. This is only compensated in part by anthropogenic creation of secondary habitats, such as different kinds of pits or coal heaps. Nevertheless, there is a strong need for restoration of dynamic habitats by floodplain revitalization and dune slack restoration.     

Entrainment of Geotropic Oscillations in Hypocotyls of Helianthus annuus– An Experimental and Theoretical Investigation

The effects of periodically repeated geotropic stimulations (geotropic pulses) on sunflower hypocotyls are studied. The experimental results agree with predictions from a theory for geotropic movements of the hypocotyl. A sunflower hypocotyl performs circumnutations around or across the plumb line with a period of about 2.5 hours. These oscillations can be entrained to periodically repeated geotropic pulses with a period in a region around 2.5 hours. The limits of this “region of entrainment’ for geotropic pulses are studied. In the region of entrainment resonance curves, i.e., the amplitude of the oscillations plotted as a function of the period of the geotropic pulses, are obtained. The phase differences (measured as time differences) between the geotropic pulse rhythms and the resulting oscillations are also studied. Beat phenomena are predicted and recorded outside the region in which the plants can be entrained. The results are discussed in relation to oscillating phenomena of circadian type (i.e., with a period close to 24 hours), and many similarities are pointed out.     

Substrate-Borne Vibration Mediates Intrasexual Agonism in the New Zealand Cook Strait Giant Weta (<Emphasis Type="Italic">Deinacrida rugosa</Emphasis>)

Substrate-borne vibrational communication is a common mode of information transfer in many invertebrate groups, with vibration serving as both primary and secondary signal channels in Orthopterans. The Cook Strait giant weta, Deinacrida rugosa (Orthoptera: Anostostomatidae), is an endangered New Zealand insect whose communication system has not been previously described. After field observations of intraspecific interactions in D. rugosa provided preliminary evidence for substrate-borne vibrational communication in the species, we sought to identify the following: vibrational signal structure, the mechanism of signal production, whether signal production is a sexually dimorphic trait, whether substrate-borne signals encode information regarding sender size, the primary social context in which vibration is utilized and finally, the function of vibrational signaling in the species. We used laser Doppler vibrometry to show that D. rugosa males produce low frequency (DF?=?37.00?±?1.63 Hz) substrate-borne vibrations through dorso-ventral tremulation. Rarely produced by females, male signals appear to target rivals while both are in the direct physical presence of a female. Tremulatory responses to playbacks were only produced by males in male-male-female trial contexts, and neither sex exhibited walking vibrotaxis to playback signals, indicating that substrate-borne vibrational signals are not likely a component of the courtship repertoire. While we found that vibrational signal structure was not closely related to signaler size, males that initiated male-male signaling bouts held a significant advantage in contests.     

Vibratory Communication in the Jumping Spider Phidippus clarus: Substrate‐borne Courtship Signals are Important for Male Mating Success

Recently, work has shown that multimodal communication is common throughout the animal kingdom but the function of multimodal signals is still poorly understood. Phidippus clarus are jumping spiders in which males produce multimodal (visual and vibrational) signals in both male–male (aggressive) and male–female (courtship) contexts. The P. clarus mating system is complex, with sex ratios and the level of male competition changing over the course of the breeding season. Vibrational signal components have been shown to function in male aggressive contests but their role in courtship has not been investigated. Here, we performed an experiment to test the role of vibrational signaling in courtship by observing mating success for males that were experimentally muted. We show that vibratory courtship signals, and in particular signaling rate, is an important component of mating success and potentially a target of female choice. While the ability to produce vibratory signals significantly increased mating success, some muted males were still able to successfully mate. In these trials, signaling rate also predicted mating success suggesting that redundant signal components may compensate for errors and perturbations in signal transmission or that vibratory signals function to enhance the efficacy of visual signals.     

Substrate-borne vibrational signals and stridulatory organs for sexual communication in leafminer,Liriomyza sativae (Diptera: Agromyzidae)

The vegetable leafminer (Liriomyza sativae [Burgess]) is a highly polyphagous pest that threatens vegetables and horticultural plants. Although sexual communication is a key component of the animal behavioral repertoire, the mechanism underlying sexual communication in L. sativae remains to be elucidated. Here, we used laser vibrometry to characterize the vibrational signals emitted by L. sativae during pair formation. By emitting trains of vibrational pulses (male calling) the male initiated communication on the host plant. The female then became immobile and responded to the male calling by emitting replies (female replies), which in turn triggered male replies consisting of a rapid series of chirps and trills. If the female replied, a continuous exchange of male and female replies ensued, representing a duet. In playback trials, a playback signal caused responses from the opposite sex. Moreover, scanning electron microscopy revealed vibration-producing stridulatory organs in both male and female individuals. The files in males were more developed than those in females, and older male specimens had more signs of abrasion. The results provide new insight into the mating biology of L. sativae.     

First Evidence of Vibrational Communication in Homotomidae (Psylloidea) and Comparison of Substrate-Borne Signals of Two Allied Species of the Genus <Emphasis Type="Italic">Macrohomotoma</Emphasis> Kuwayama

Substrate-borne signals are widely used in Hemiptera and are known to be utilized in mate searching and recognition. Within this Order, the superfamily Psylloidea is a diverse taxon which uses this type of signal modality during mating behavior between the two sexes. This study describes and compares the previously unreported vibrational communication of two closely related species of Macrohomotoma (Homotomidae). Both genders of these two species, Macrohomotoma gladiata Kuwayama 1908 and Macrohomotoma robusta Yang 1984, emit vibrational signals and establish duets during mating. The structure of male calling consists of two chirps while the female response is a single chirp. Males may sometimes follow the female response by emitting a single chirp that sounds similar to the female response with respect to the chirp duration and dominant frequency. This behavior is novel among Psylloidea and its potential function is discussed. Specific comparison of signal characteristics has revealed that the two species of Macrohomotoma are clearly distinguishable from each other which opens the possibility of acoustic signals being used for species delineation.     

Tremulatory and Abdomen Vibration Signals Enable Communication through Air in the Stink Bug Euschistus heros

Communication by substrate-borne mechanical signals is widespread among animals but remains one of their least understood communication channels. Past studies of vibrational communication in insects have been oriented predominantly to communication during mating, showing that species- and sex-specific vibrational signals enable recognition and localization of potential mates on continuous solid substrates. No special attention has been paid to vibrational signals with less obvious specificity as well as to the possibility of vibrational communication across substrates that are not in physical contact. We aimed to reinvestigate emission of the aforementioned vibrational signals transmitted through a plant in the stink bug Euschistus heros (Pentatomidae: Pentatominae) and to check whether individuals are able to communicate across adjecent, physically separated substrates. We used laser vibrometry for registration of substrate-borne vibrational signals on a bean plant. Using two bean plants separated for 3 to 7 cm between two most adjacent leaves, we investigated the possibility of transmission of these signals through air. Our study showed that males and females of E. heros communicate using tremulatory, percussion and buzzing signals in addition to the previously described signals produced by vibrations of the abdomen. Contrary to the latter, the first three signal types did not differ between sexes or between pentatomid species. Experiments with two physically separated plants showed significant searching behaviour and localization of vibrational signals of an E. heros male or a female, in response to abdominal vibration produced signals of a pair duetting on the neighbouring plant, in comparison to control where no animals were on the neighbouring plant. We also confirmed that transmission through air causes amplitude and frequency decay of vibrational signals, which suggests high-amplitude, low-frequency tremulatory signals of these stink bugs their most plausible way of communication across discontinuous substrates.     

Vibration‐mediated territoriality in the warty birch caterpillar Drepana bilineata

Abstract The warty birch caterpillar Drepana bilineata produces two distinct types of vibrational signals (mandible drumming and anal scraping) during interactions with conspecifics. Vibrational signalling is characterized using standard and high‐speed videography synchronized with laser‐doppler vibrometry, and behavioural experiments test the hypothesis that signalling functions to advertise occupancy of birch (Betula) leaves. Drumming involves raising the head and striking the leaf with the sharp edges of the open mandibles. Anal scraping involves dragging a pair of specialized oar‐shaped setae against the leaf surface. Staged encounters between leaf residents and conspecific intruders result in the resident signalling, with rates increasing as the intruder moves closer. Intruders signal significantly less often than residents. Conflicts are typically resolved within a few minutes, with the resident winning in 61% of the trials, and the intruder winning in 6%. Contests that last more than 30 min are deemed ‘ties’ and comprise the remaining 33% of trials. The results support the hypothesis that vibrational signals function to advertise leaf occupancy. Vibrational communication is believed to be widespread in Drepanoidea caterpillars, but has only been described in two species to date: D. bilineata (present study) and Drepana arcuata. It is proposed that differences in territorial behaviour and signalling between these species are related to their relative investments in silk leaf mats and shelters. The proximate and ultimate bases for the evolution of vibrational communication in caterpillars are discussed.     

Behavioral and electrophysiological evidences that the lateral line is involved in the inter-sexual vibrational communication of the himé salmon (landlocked red salmon,Oncorhynchus nerka)

Characteristic vibrational signals are suggested to be exchanged between the sexes during the spawning behavior in the himé salmon (landlocked red salmon, Oncorhynchus nerka). To check whether the lateral line is used to detect and process these vibrational signals, we examined how Co²⁺, which is known to block the mechano-electrical transduction in the lateral line detector, affects both the spawning behavior and lateral line response of the male himé salmon. The results showed that Co²⁺ blocked both the spawning behavior towards the vibrating model (Fig. 2) and the lateral line response to the vibrational stimuli (Figs. 5, 6), if the fish were forced to swim in the water containing 1.0 mM Co²⁺ for 1 to 1.5 h or longer in the presence of 0.25 mM Ca²⁺. 0.1 mM Co²⁺ had similar but weaker effects. These results indicate that the vibrational signals from the vibrating model are detected and processed by the lateral line system to elicit the spawning behavior. These are the first experimental evidences that the lateral line sense is involved in the communicational behavior of the fish.     

A Taxonomic Study of Korean Tetrigidae (Orthoptera: Caelifera: Tetrigoidea)

A Taxonomic study of Korean Tetrigidae (Orthoptera: Caelifera: Tetrigoidea) is revised. Twelve species are recognized including two species (Tetrix silvicultrix Ichikawa and T. minor Ichikawa) recorded for the first time in Korea. Keys and photographs of habitus for species are provided.     

Jamaican Field Cricket Mate Attraction Signals Provide Age Cues

Older males often have a mating advantage, either resulting from the fact that they live longer or resulting from the fact that they both live longer and signal this to females. Male field crickets signal acoustically to attract potential mates. Some field cricket mating signals provide cues about male age while others do not. We explored whether male Jamaican field crickets, Gryllus assimilis, mating signals change with age. Our results show that older males produce chirps with longer pulses, more pulses, at higher pulse and chirp rates, and their chirps are both longer and louder than those produced by younger males. Our findings suggest that Jamaican field cricket mating signals provide cues about male age, explaining between 10% and 54% of the variation in signaling traits. Females might be able to use these mating signal differences to distinguish between older and younger mates.     

Divergence in Female Duetting Signals in the Enchenopa binotata Species Complex of Treehoppers (Hemiptera: Membracidae)

Sexual communication often involves signal exchanges between the sexes, or duetting, in which mate choice is expressed through response signals. With both sexes acting as signalers and receivers, variation in the signals of males and females may be important for mate choice, reproductive isolation, and divergence. In the Enchenopa binotata species complex – a case study of sympatric speciation in which vibrational duetting may have an important role – male signals are species‐specific, females choose among males on the basis of signal traits that reflect species and individual differences, and female preferences have exerted divergent selection on male signals. Here, we describe variation in female signals in the E. binotata species complex. We report substantial species differences in the spectral and temporal features of female signals, and in their timing relative to male signals. These differences were similar in range to differences in male signals in the E. binotata complex. We consider processes that might contribute to divergence in female signals, and suggest that signal evolution in the E. binotata complex may be influenced by mate choice in both sexes.     

Assessing Condition-dependence of Male Flash Signals in <Emphasis Type="Italic">Photinus</Emphasis> Fireflies

Females often show a preference for exaggerated male sexual traits or courtship behaviors. Such preferences can benefit females if trait expression is correlated with male genetic quality or phenotypic condition. Previous studies of several Photinus fireflies have revealed considerable intraspecific variation in the bioluminescent courtship signals emitted by males, and have also demonstrated that females prefer more conspicuous male signals. Thus, females might gain information about male phenotypic quality if courtship signals reflect male condition. We examined possible condition-dependence of Photinus male courtship signals using two complementary approaches. First we experimentally manipulated male mating status, which is expected to affect male condition by depleting resources required for nuptial gift formation, and looked at how individual male flash signals changed with mating status and over time. We used an additional approach to assess condition-dependence by examining whether a relationship exists between flash signal parameters and measures of male condition and body shape. We found that the pulse rate of P. greeni courtship signals was not altered by male mating status or age, and that the pulse duration of P. ignitus signals was also not affected by male mating status. In P. pyralis fireflies, males showed a non-significant trend toward reduced signal pulse duration with age. When we examined the relationship between male flash signals and condition measures, we found no effect of male condition or body shape on courtship signals in P. greeni or P. ignitus; in P. pyralis, males with wider body shapes produced longer duration flash signals. On the other hand, we found no evidence in P. pyralis that condition predicted flash duration. Taken together, these results indicate that Photinus males’ flash signals do not reflect adult male condition, and suggest that females are unlikely to use courtship signals as an indicator of male phenotypic quality.     

Interactional behaviors of the parasitic beetle Paussus favieri with its ant host Pheidole pallidula: the mimetic role of the acoustical signals

The social parasitic beetle Puussus favieri(Coleoptera,Carabidae,Paussini)performs different types of stridulations,which sclectively mimic those emitted by dif-ferent ant castes of its host Pheidole pallidula(Hymenoptera,Formicidae,Myrmicinae).However,the significance of this acoustical mimicry for the success of the parasitic strat-egy and the behaviors elicited in the host ants by stridulations was unknown.We reared Paussus favieri in Pheidole pallidula colonies and filmed their interacting behaviors.We analyzed in slow motion the behavior of ants near a stridulating beetle.We analyzed sep-arately trains of pulse(Pa+Pb,produced by repeated rubbings)and single pulse(Pc,produced by a single rubbing)of stridulations,clearly recognizable from the shaking up and down of the beetle hind legs.and associated them with differcent ant responscs.The full repertoire of sounds produced by P:favieri elicited benevolent responses both in workers and soldiers.We found that different signals elicit different(sometimes multiplc)bchaviors in ants,with different frequency in the two ant castes.However,Pc(alone or in conjunction with other types of pulses)appears to be the type of acoustic signal mostly responsible for all recorded behaviors.These results indicate that the acoustic channel plays a pivotal role in the host-parasite interaction.Finding that a parasite uses the acoustical channel so intensively,and in such a complicated way to trigger ant bchaviors,indicates that acoustic signals may be more important in ant societies than commonly recognized.