The secret stridulatory file under the right tegmen in katydids (Orthoptera, Ensifera, Tettigonioidea)

Differentiation between left and right wing stridulatory files in the field cricket Gryllus bimaculatus (Orthoptera: Gryllidae)

Male crickets produce acoustic signals by wing stridulation, attracting females for mating. A plectrum on the left forewing's (or tegmen) anal margin rapidly strikes along a serrated vein (stridulatory file, SF) on the opposite tegmen as they close, producing vibrations, ending in a tonal sound. The tooth strike rate of the plectrum across file teeth is equal to the sound frequency produced by the cricket (i.e., ∼5k teeth/s for ∼5 kHz in field crickets) and is specific to the forewing's resonant frequency. Sound is subsequently amplified using specialised wing cells. Anatomically, the forewings appear to mirror each other: both tegmina bear a SF and plectrum; however, most cricket species stridulate using right-over-left wing overlap making the stridulatory mechanism asymmetrical by default, rendering the left tegmen's SF unused. Therefore, we hypothesised structural differences between functional and unfunctional SFs. Three-dimensional mapping was used to accurately measure SF structures in Gryllus bimaculatus wings. We found that the left SF shows significantly greater variation in inter-tooth distance than the right, but less variation within the first sixty teeth (the functional part) than the right file. The left SF's slow evolutionary change over millions of years is discussed considering modern molecular phylogenies and fossil records.

Bioacoustics and systematics of Mecopoda (and related forms) from South East Asia and adjacent areas (Orthoptera, Tettigonioidea, Mecopodinae) including some chromosome data

Bush-crickets (or katydids) of the genus Mecopoda are relatively large insects well-known for their sounds for centuries. Bioacoustic studies in India and China revealed a surprisingly large diversity of sound patterns. We extend these studies into the tropics of South East Asia using integrative taxonomy, combining song analysis, morphology of sound producing organs and male genitalia as well as chromosomes, to get a better understanding of the phylogeny and evolution of this widespread group. Besides the closely related genus Eumecopoda, the genus Mecopoda contains some isolated species and a large group of species which we assign to the Mecopoda elongata group. Some species of this group have broad tegmina and stridulatory files with different tooth spacing patterns and produce continuous, often relatively complicated, trill-like songs. The species of another subgroup with narrower wings have all similar files. Their songs consist of echemes (groups of syllables) which differ in syllable number and syllable repetition rate and also in echeme repetition rate. Our results show that South East Asia harbours a large and certainly not yet fully explored number of Mecopoda species which are most easily and clearly identified by song. Based on the data, five new forms are described: Mecopoda mahindai Heller sp. nov., Mecopoda paucidens Ingrisch, Su Heller sp. nov., Mecopoda sismondoi Heller sp. nov., Mecopoda niponensis vietnamica Heller Korsunovskaya subsp. nov., Eumecopoda cyrtoscelis zhantievi Heller subsp. nov. In addition, some taxonomic changes are proposed: Eumecopoda Hebard, 1922 stat. rev., Paramecopoda Gorochov, 2020, syn. nov. of Eumecopoda Hebard, 1922, Mecopoda javana (Johansson, 1763) stat. nov. (neotype selected) with M. javana minahasa Gorochov, 2020 stat. nov., M. javana darevskyi Gorochov, 2020 stat. nov., M. javana buru Gorochov, 2020 stat. nov., Mecopoda macassariensis (Haan, 1843) stat. rev., Mecopoda ampla malayensis Gorochov, 2020 syn. nov., Mecopada ampla javaensis Gorochov, 2020 syn. nov., Mecopoda fallax aequatorialis Gorochov, 2020 syn. nov., the last three are all synonyms of Mecopoda himalaya Liu, 2020, Mecopoda yunnana Liu 2020, stat. nov.

Functional morphology of tegmina-based stridulation in the relict species Cyphoderris monstrosa (Orthoptera: Ensifera: Prophalangopsidae)

Male grigs, bush crickets and crickets produce mating calls by tegminal stridulation: the scraping together of modified forewings functioning as sound generators. Bush crickets (Tettigoniidae) and crickets (Gryllinae) diverged some 240 million years ago, with each lineage developing unique characteristics in wing morphology and the associated mechanics of stridulation. The grigs (Prophalangopsidae), a relict lineage more closely related to bush crickets than to crickets, are believed to retain plesiomorphic features of wing morphology. The wing cells widely involved in sound production, such as the harp and mirror, are comparatively small, poorly delimited and/or partially filled with cross-veins. Such morphology is similarly observed in the earliest stridulating ensiferans, for which stridulatory mechanics remains poorly understood. The grigs, therefore, are of major importance to investigate the early evolutionary stages of tegminal stridulation, a critical innovation in the evolution of the Orthoptera. The aim of this study is to appreciate the degree of specialization on grig forewings, through identification of sound radiating areas and their properties. For well-grounded comparisons, homologies in wing venation (and associated areas) of grigs and bush crickets are re-evaluated. Then, using direct evidence, this study confirms the mirror cell, in association with two other areas (termed 'neck' and 'pre-mirror'), as the acoustic resonator in the grig Cyphoderris monstrosa Despite the use of largely symmetrical resonators, as found in field crickets, analogous features of stridulatory mechanics are observed between C. monstrosa and bush crickets. Both morphology and function in grigs represents transitional stages between unspecialized forewings and derived conditions observed in modern species.