Ultrasonic production and its reception in some neotropical Tettigoniidae.

Ultrasonic production and its reception in four species of neotropical grasshoppers were studied. Phlugis sp. 1 and P. sp. 2 moved the forewings at the rate of 35 to 40 and 40 to 45/sec and produced sounds by closing motion of the wings. The stridulatory sounds dominantly included 44–50 and 46–56 kc/s, respectively. The audible components were scarcely included. The rate of tooth-pulses which were caused by impact between the teeth and the scraper was about 650/sec for P. sp. 1 and about 800/sec for P. sp. 2. The intensity of the stridulation was 100 to 110 dB (re 0·0002 dyn/cm2) at about 10 cm from the dorso-lateral side of the insect. Drepanoxiphus modestus (Bruner) emitted stridulatory sounds by closing the forewings. As distinct from Phlugis, the tooth-pulses fused each other into a pure tone pulse of 22–24 kc/s. The intensity was 98 to 102 dB at 10 cm distance. Conocephalus saltator (Saussure) moved the wings at a rate of 30/sec and made sounds by both opening and closing movements of the forewings. The sound produced by opening the wings was about 20 dB less intense than that by closing and strongly included the frequencies 18–42 kc/s, whereas the dominant frequencies of the sound during closing was about 40 and 60–66 kc/s. The optimum sensitivity of the tympanic organs of these species was between 20 and 25 kc/s. The minimum threshold was about 30 dB for C. saltator and about 40 dB for the other three species. In all four species, the central auditory large fibres which lie between the brain and metathoracic ganglion received excitatory input from the ipsilateral tympanic nerve and inhibitory input from the contralateral tympanic nerve.