No abstract

Troglophilus neglectus (Gryllacridoidea, Raphidophoridae) is a nocturnal Ensifera which can be found in caves of Slovenia. The anatomy of the tibial organs in the fore-, mid-, and hindlegs, as well as the external morphology of the proximal fore-tibia and the prothoracic tracheal system, is described comparatively. In the prothorax and in the forelegs, no sound-conducting structures such as an acoustic trachea, enlarged spiracles, or tympana are developed. A group of 8-10 campaniform sensillae is located in the dorsal cuticle of the proximal tibia. In each leg, the tibial organ complex is built up by two scolopale organs, the subgenual organ and the intermediate organ; the structure and the number of scolopidia is similar in each leg. No structure resembling the crista acoustica is found. The subgenual organ contains around 30 scolopidia; the intermediate organ is subdivided into a proximal part containing 8-9 scolopidia and a distal part with 5-6 scolopidia. The two groups of scolopidia are not directly connected to the tracheal system. The tibial organs in the forelegs are insensitive to airborne sound, and they appear to be more primitive compared to those found in members of the Tettigoniidae and the Gwllidae. The results indicate that the complex tibial organs in all legs of T. neglectus are primarily vibrosensitive. © 1995 Wiley-Liss, Inc.

The transmission characteristics of the acoustic tracheae in the forelegs of seven tettigoniid species were investigated by sinusoidal analysis. The species were selected to represent a range of body sizes and leg lengths. Four subfamilies were included, with two species each from three of them; the tracheae in such closely related pairs could be expected to be similar in shape despite their different dimensions. The tracheae were dissected out for morphometric analysis and compared with one another with respect to their overall dimensions and those of typical subsections. The amplitude-versus-frequency response of acoustic transmission in the tracheae was measured at various positions with a probe microphone. The stimuli were continuous sinusoidal signals at an intensity of 100 or 110 dB SPL. The tracheae of all the species studied here (in males and females) are distinguished by a bandpass-limited transmission characteristic. In the frequency range above 5 kHz (at least to 40 kHz) the sound signals are amplified by 10-15 dB during passage through the tracheae. These results are compared with the threshold curves of the auditory organs and the spectra of the conspecific songs. Although in some cases there are considerable differences in the dimensions of the tracheae, the transmission characteristics are very similar; no specific adaptations to the frequency composition of the conspecific song were found.

The morphology and the physiology of the auditory receptor organs in the forelegs of the tettigoniid species Gampsocleis gratiosa were investigated in detail. According to the tonotopic organization of the receptor cells of the crista acoustica in bushcrickets the threshold curves of all receptors found in the organs were correlated with the morphology of the auditory receptor cells. This was done by arranging them in relation to their frequency tuning with the receptors along the chain of cells in both organs starting proximally with the extreme low frequency cell up to the highest ultrasonic cells a t the distal end of the crista acoustica.This investigation reveals that the auditory receptor organs of Gampsocleis gratiosa possess a broad banded hearing threshold curve including very low frequency parts. Also the conspecific stridulatory song is very broad banded with extraordinarily low frequency components. Therefore the sender and the receiver of this species-specific communication system seem to be well adapted to each other. o 1993 Wiley-Liss, Inc.

In Locusta migratoria and Schistocerca gregaria, the projection areas and branching patterns of the tympanal receptor cells in the thoracic ganglia were revealed. Four auditory neuropiles can be distinguished on each side of the ventral cord, always located in the anterior part of the ring tract in each neuromere (two in the meta-, one in the meso-, and one in the prothoracic ganglion). Some of the receptor fibres ascend to the suboesophageal ganglion. There are distinct subdivisions within the auditory, frontal metathoracic and mesothoracic neuropiles. The arrangement of the terminal arborisations of the four types of tympanal receptor cells according to their different frequency-intensity responses is somatotopic and similar in the two ganglia. Here the receptor cells of type-1 form a restricted lateroventral arborisation. Cells of type-4 occupy the caudal part with a dorsorostral extension. Cells of type-2 and -3 arborise in a subdivision between both. Most of the stained low-frequency receptors (type-1, -2, and -3) terminate either in the metathoracic or, predominantly, in the mesothoracic ganglion. In contrast, the high-frequency cells (type-4) ascend to the prothoracic ganglion. The receptor fibres of the different types of receptor cells differ in diameter.