Search for: All records

ABSTRACT Male alternative reproductive tactics are taxonomically widespread, with many species showing males with distinctly different phenotypic characters such as body size or weaponry. Several mechanisms can drive the expression of these male morphs, including genetic polymorphism or environmental interactions during development. In insects, multiple male morphs are common in several orders, including Coleoptera, Odonata, and Hymenoptera, but are rare in Orthoptera. This study establishes the presence of two male phenotypic morphs in the bush cricketSatizabalus jorgevargasi, a species in which the males display mandibular weaponry, and tests the effects of diet on the expression of male dimorphic characters. Male nymphs were raised under standard conditions until adulthood, whereupon morphological measurements were taken. Males raised under standard conditions showed two male phenotypes on the basis of head size and body colouration—a major morph with larger heads and more colouration, and a smaller and duller minor morph. A second group of male nymphs were housed individually and fed either a high‐protein diet or a high‐carbohydrate diet. Body weight and pronotum length were measured on a weekly basis as the nymphs developed, and once the males had matured, morphological and bioacoustic characters were measured. Diet had a significant impact on these male dimorphic characters, with protein‐fed males having significantly larger heads and mandibles. Additionally, males reared on the high‐protein diet had significantly more regions with colour when compared to carbohydrate‐fed males. Our data parallel that seen in other invertebrate groups, where higher levels of protein during maturation are key to the production of larger male morphs. 

Abstract Male crickets sing to attract females for mating. Sound is produced by tegminal stridulation, where one wing bears a plectrum and the other a wing vein modified with cuticular teeth. The carrier frequency (fc) of the call is dictated by the wing resonance and the rate of tooth strikes. Therefore, the fc varies across species due to the size of the vibrating membranes on the wings and/or the speed of tooth strikes. But how well is the resonant frequency (fo) conserved in dried preserved specimens? This project is designed to investigate the gradual change in cricket wing fo over time and aims to produce equations that help to predict or recover the original natural frequency of wing vibration in dry-preserved crickets and allies. Using laser Doppler vibrometry, we scanned the wings of living specimens to determine their fo. The specimens were then preserved, allowing us to continue measuring the wings fo as they desiccate. We found that after the first week, fo increases steeply, reaching a plateau and stabilizing for the following months. We go on to propose a model that can be used to recover the original fc of the wings of preserved Ensifera that use pure tones for communication. Models were corroborated using preserved specimens previously recorded and mounted in dry collections for more than 10 years. 

Mammalian hearing operates on three basic steps: 1) sound capturing, 2) impedance conversion, and 3) frequency analysis. While these canonical steps are vital for acoustic communication and survival in mammals, they are not unique to them. An equivalent mechanism has been described for katydids (Insecta), and it is unique to this group among invertebrates. The katydid inner ear resembles an uncoiled cochlea, and has a length less than 1 mm. Their inner ears contain a hearing organ,crista acustica, which holds tonotopically arranged sensory cells for frequency mapping via travelling waves. Thecrista acusticais located on a curved triangular surface formed by the dorsal wall of the ear canal. While empirical recordings show tonotopic vibrations in the katydid inner ear for frequency analysis, the biophysical mechanism leading to tonotopy remains elusive due to the small size and complexity of the hearing organ. In this study, robust numerical simulations are developed for anin silicoinvestigation of this process. Simulations are based on the precise katydid inner ear geometry obtained by synchrotron-based micro-computed tomography, and empirically determined inner ear fluid properties for an accurate representation of the underlying mechanism. We demonstrate that the triangular structure below the hearing organ drives the tonotopy and travelling waves in the inner ear, and thus has an equivalent role to the mammalian basilar membrane. This reveals a stronger analogy between the inner ear basic mechanical networks of two organisms with ancient evolutionary differences and independent phylogenetic histories. 

Stridulation is used by male katydids to produce soundviathe rubbing together of their specialised forewings, either by sustained or interrupted sweeps of the file producing different tones and call structures. There are many species of Orthoptera that remain undescribed and their acoustic signals are unknown. This study aims to measure and quantify the mechanics of wing vibration, sound production and acoustic properties of the hearing system in a new genus of Pseudophyllinae with taxonomic descriptions of two new species. The calling behaviour and wing mechanics of males were measured using micro-scanning laser Doppler vibrometry, microscopy, and ultrasound sensitive equipment. The resonant properties of the acoustic pinnae of the ears were obtainedviaμ-CT scanning and 3D printed experimentation, and numerical modelling was used to validate the results. Analysis of sound recordings and wing vibrations revealed that the stridulatory areas of the right tegmen exhibit relatively narrow frequency responses and produce narrowband calls between 12 and 20 kHz. As in most Pseudophyllinae, only the right mirror is activated for sound production. The acoustic pinnae of all species were found to provide a broadband increased acoustic gain from ~40–120 kHz by up to 25 dB, peaking at almost 90 kHz which coincides with the echolocation frequency of sympatric bats. The new genus, namedSatizabalusn. gen., is here derived as a new polytypic genus from the existing genusGnathoclita, based on morphological and acoustic evidence from one described (S. sodalisn. comb.) and two new species (S. jorgevargasin. sp. andS. haucan. sp.). Unlike most Tettigoniidae,Satizabalusexhibits a particular form of sexual dimorphism whereby the heads and mandibles of the males are greatly enlarged compared to the females. We suggest thatSatizabalusis related to the genusTrichotettix, also found in cloud forests in Colombia, and not toGnathoclita. 

This study focuses on the genusDioncomenaand its acoustics, particularly the unique songs produced by maleDioncomenathat consist of several distinct elements in a fixed sequence, culminating in a coda that typically elicits a response from a receptive female. We also examine the inflated pronotal lobes, which we term prebullae, that are prominently developed in someDioncomenaspecies but not in others. We discuss the role of prebullae in the context of acoustic communication inDioncomenaand other related Phaneropterini genera that have similar lateral pronotal lobes. We found that prebullae size is correlated with habitat distribution, with larger prebullae occurring in isolated species while aggregation-prone species have smaller or less pronounced prebullae. Using micro-computer tomography we show sexual dimorphism in the 3D geometry of the acoustic tracheae, being larger in the male. Interestingly, the tracheae are coupled by a septum, like in field crickets, which suggests potential cross talk. We define three groups ofDioncomenabased on altitude preferences, ecology, color patterns, and songs: thejagoi-,tanneri-, andornata-groups. We describe the songs of several species, including newly identified species such asD. flavoviridissp. nov.,D. magomberasp. nov.,D. ngurumontanasp. nov.,D. sanjesp. nov.,D. tanneri,D. versicolorsp. nov., andD. zernyi. We also provide information on the nymphs, development time, and mating behavior of various species reared in the laboratory, shedding light on their phenology and adaptations to their habitats.