Bidirectional communication system in katydids: the effect on chorus structure

Unlike most acoustic systems evolved for pair formation whereonly males signal, the katydidPhaneroptera nana has a bidirectional communication system where both males and females sing. Despiteextensive study on male chorusing behavior in different communicationsystems, this behavior has rarely been explored in duettingspecies. I examined how this bidirectional communication systemaffects the collective pattern of male signaling.P. nana malesalternate their songs, and in response to synthetic stimulidelay their calls, according to the phase of stimulation. Pairsof synthetic calls (simulating alternating males) presentedto females elicited equal female response, as long as the intercallinterval was 200 ms. Thus, male alternation is imposed by thefemale's responsiveness and may be interpreted as a "jammingavoidance reaction." Further evidence suggests that chorusstructure is not merely constrained by the female sensory temporalresolution, but rather is adaptively related to female choicein this species.     

Increase in song frequency decreases spermatophore size: correlative evidence of a macroevolutionary trade-off in katydids (Orthoptera: Tettigoniidae)

In many katydids, the male feeds his mate with a large gelatinous spermatophore. Males of most species also produce elaborate calling songs. We predicted a negative relationship between spermatophore size and call frequency because of trade-offs between these two costly traits. Our comparative analysis controlling phylogeny and body size supported this prediction. Although call frequency is expected to decrease with increasing body size, after controlling for phylogeny, both variables were not related. Finally, given that song frequency and spermatophore size are likely targets of sexual selection, we examined the relationship between these variables and sexual size dimorphism (SSD) which can be influenced by sexual selection on body size. We found that only female body size was positively related to SSD, suggesting that natural and/or sexual selection on female body size may be stronger than sexual selection on male and spermatophore size.     

Singers in the grass: call description of conehead katydids (family: Tettigoniidae) and observations on avoidance of acoustic overlap

ABSTRACT

The sub-family Conocephalinae constitutes one of the richest groups of katydids in terms of diversity and distribution. Tropical katydids especially in India have largely escaped academic attention. Here, we record and describe call patterns for six conehead katydids from India: Conocephalus melanus, Conocephalus sp X, Euconocephalus indicus, Euconocephalus mucro, and Euconocephalus sp Y from North-Eastern Himalayas and Euconocephalus pallidus from the Western Ghats. All the species showed broadband frequency spectra (10.5–42.4 kHz), and three of the six species showed high rates of calling (289–453 syllables/s). We observed that the co-occurring call types never called at the same time or from the same location. We hypothesized this partitioning between call types is due to similarity in their calls; we used non-metric multi-dimensional scaling (NMDS) to investigate patterns of temporal or habitat-partitioning that some of the co-occurring call types exhibited during the course of study. The co-occurring Euconocephalus sp Y and E. mucro with high degree of overlap and similarity in their calls exhibited partitioning on a spatial scale. Conocephalus sp. X and C. melanus with distinct calling activity peaks formed separate clusters based on temporal call structures. As females rely heavily on spectral qualities, we speculate partitioning on temporal scale to avoid heterospecific interference due to similar spectral properties between the two call types.     

Acoustic mimicry and disruptive alternative calling tactics in an Australian bushcricket (Caedicia; Phaneropterinae; Tettigoniidae; Orthoptera): does mating influence male calling tactic?

Abstract.  Male calling and searching tactics are described for a duetting Australian bushcricket, Caedicia sp. 12 (Phaneropterinae; Tettigoniidae; Orthoptera). The repertoire of Caedicia sp. 12 consists of the calling song and, by nonduetting males, a series of calling tactics that include short-click calling, disruptive over-singing and a call mimicking the entire duet. Nonduetting males respond to the production of a duet by another male and a female with short-click calls that mimic the female call at the conclusion of a duet. By manipulating the male's mating history, it is found that this form of calling behaviour is more likely to occur within the male's 6-day postmating refractory period; the low cost tactic allows males to re-mate during spermatophore replenishment. Males also produce disruptive calls in response to a duet, where the male may over-sing the duetting male's signal or produce a call that appears to mimic the entire duet; the male produces a calling song followed by a short signal that has the same latency as the female's reply within a duet. Males also over-sing crucial elements of the duetting-male's song that are normally critical for the female's conspecific recognition. There is no evidence that females search for the duetting male partner, but males unable to enter a duet will search for the call of a responding female. Searching by males is more common when these males are producing disruptive calls. Alternative male calling tactics are discussed as a set of conditional strategies for securing unmated females.     

Increases in egg production in multiply mated female bushcrickets Leptophyes punctatissima are not due to substances in the nuptial gift

Abstract. 1. A positive effect of the degree of polyandry on egg production is widespread in insects, particularly in species in which the male provides a nuptial gift.
2. This study aimed to determine whether or not this effect is due to females using nutrients from the nuptial gift (spermatophore and spermatophylax) to manufacture more eggs in the bushcricket Leptophyes punctatissima .
3. Females were permitted either a single or a double mating (with two different males) and, in both mating categories, were either prevented from consuming any part of the spermatophore or were permitted to consume the entire spermatophore.
4. Doubly mated females were found to lay over twice as many eggs over a 4-week period compared with singly mated females. This difference did not appear to be caused by the consumption of extra nuptial gift material: mating was found to have a significant positive effect on the number of eggs laid, while nuptial gift feeding had no effect.     

AUTOMATIC ACOUSTIC IDENTIFICATION OF SINGING INSECTS

ABSTRACT

We report on our research efforts towards developing efficient equipment for the automatic recognition of insects using only the acoustic modality. Specifically, we deal with three groups of insects, namely the crickets, cicadas and katydids. Inspired by well-documented tactics of speech processing, the signal processing employed in the present work is elaborated further with respect to the sound production mechanisms of insects. In order to improve the practical efficacy of our equipment, we adopt a score-level fusion of classifiers with non-parametric (probabilistic neural network) and parametric (Gaussian mixture models) estimation of the probability density function. An efficient hierarchic classification scheme is introduced, where the identification of unlabelled input takes place at various levels of hierarchy, such as suborder, family, subfamily, genus and species. We evaluate the practical significance of our approach on a large and well-documented catalogue of recordings of crickets, cicadas and katydids. For the hierarchic classification scheme, we report identification accuracy that exceeds 99% at suborder and family levels. In the straight classification scheme, we report accuracy of 90% for 307 species.     

Conservation of orthopteran biological diversity relative to landscape change in temperate Eurasia

This paper discusses orthopteran conservation in temperate and subtropical Eurasia. Distribution patterns of the orthopteran centres of diversity and endemism are described. Eleven main areas of diversity and endemism are identified. The majority of rare taxa are associated with these areas. The distribution of protected areas is discussed in relation to orthopteran conservation. Some proposals for inclusion or exclusion of certain orthopteran species on the IUCN and national Red Lists are debated. Emphasis is given to landscape heterogeneity and ecosystem mosaics for orthopteran biodiversity conservation.     

Sensory-based niche partitioning in a multiple predator–multiple prey community

Many predators and parasites eavesdrop on the communication signals of their prey. Eavesdropping is typically studied as dyadic predator–prey species interactions; yet in nature, most predators target multiple prey species and most prey must evade multiple predator species. The impact of predator communities on prey signal evolution is not well understood. Predators could converge in their preferences for conspicuous signal properties, generating competition among predators and natural selection on particular prey signal features. Alternatively, predator species could vary in their preferences for prey signal properties, resulting in sensory-based niche partitioning of prey resources. In the Neotropics, many substrate-gleaning bats use the mate-attraction songs of male katydids to locate them as prey. We studied mechanisms of niche partitioning in four substrate-gleaning bat species and found they are similar in morphology, echolocation signal design and prey-handling ability, but each species preferred different acoustic features of male song in 12 sympatric katydid species. This divergence in predator preference probably contributes to the coexistence of many substrate-gleaning bat species in the Neotropics, and the substantial diversity in the mate-attraction signals of katydids. Our results provide insight into how multiple eavesdropping predator species might influence prey signal evolution through sensory-based niche partitioning.     

Agonistic communication between males of a zaprochiline katydid (Orthoptera: Tettigoniidae)

The calls produced by male katydids serve to attract femalesand repel rivals. Males generally exhibit overt aggressive responsesto conspecifics that call within their territories, and intermalespacing is maintained by properties of the call. Here we examinethe acoustic behavior of a zaprochiline katydid in which maleaggressive behavior and even the ability to detect conspecificsappear greatly reduced. Despite reduced hearing sensitivity,males were shown to detect and respond to the calls of conspecificsusing substrate-borne vibrations. During playback experimentsmales increased their calling rates by decreasing the intervalbetween chirps. However, rather than exhibit overt aggressionmales would simply change their calling sites when the intensityof playback song was increased. These results were supportedby observations of natural encounters between males in the field.The interval between chirps decreased as the distance betweencalling males decreased, and encounters were always terminatedwhen one male moved away from the other. We suggest that theloss in auditory sensitivity and reduced aggressive behaviorof this species may be a consequence of the necessity to aggregatearound highly localized feeding sites.