Fiddler on the Tree - A Bush-Cricket Species with Unusual Stridulatory Organs and Song
Insects of the order Orthoptera are well-known for their acoustic communication. The structures used for this purpose show a high diversity which obviously relates to differences in song parameters and to the physics of sound production. Here we describe song and morphology of the sound producing organs of a tropical bush-cricket, Ectomoptera nepicauda, from East Africa. It has a very unusual calling song consisting of frequency-modulated, pure-tone sounds in the high ultrasonic range of 80 to120 kHz and produced by extremely fast wing movements. Concerning morphology, it represents the most extreme state in the degree of left-right fore-wing differentiation found among Orthoptera: the acoustic parts of the left fore-wing consist exclusively of the stridulatory file, comparable in function to the bow of a violin, while the right wing carries only the plectrum ( =  string) and mirror ( =  soundbox).
Review of the East African species of the phaneropterine genus Parapyrrhicia Brunner von Wattenwyl, 1891 (Insecta: Orthoptera): secret communication of a forest-bound taxon
The East African species of Parapyrrhicia Brunner von Wattenwyl, 1891, are reviewed. Beside the description of five new species from the West Usambara, Udzungwa, Uluguru Mountains, and coastal Tanzania and the male of P. zanzibarica Brunner von Wattenwyl, 1891, data on habitat, morphology, acoustics, and the chromosomes are provided. A key to the species of Parapyrrhicia is provided. Eulioptera zanzibarica Brunner von Wattenwyl, 1891, is synonymized with Parapyrrhicia zanzibarica Brunner. All species have stridulatory files with intertooth intervals decreasing from anal to basal and low duty cycle calling songs (four species recorded) consisting of very short, narrow-banded, resonant syllables. Parapyrrhicia species showed a plesiomorphic karyotype with a diploid chromosome number of 2n = 31 and a X0 sex chromosome system in males. All species are restricted to closed wet forest areas and thus ideal organisms to be used for monitoring habitat quality of an area since they act as indicators for indigenous wet forest communities. Morphological sister pairs suggest recent speciation processes in coastal and lowland wet forests of East Africa.
Calculation of and Errors in the Susceptibility
The measurement of the susceptibility requires three measurements, two of which have to be performed with a substance of known susceptibility. The difference of these last two measurements furnishes the proportionality constant of the apparatus, always employing the same volume, while the difference with the unknown substance gives the required susceptibility.