Tettigonia viridissima

The loud calling song, produced mainly in the late afternoon and after dark, consists of sequences of closely spaced disyllabic echemes. The echeme repetition rate depends on temperature: 10-15/s is common, but in high daytime tempertaures the rate may increase to 20/s and on cool nights may be as low as 5/s. Typically the echeme sequences are interrupted at irregular intervals by very short pauses (Figs 188-190), usually of less than a second and sometimes, at high temperatures, as short as 0.2-0.3 s. Occasionally, long echeme-sequences are produced without even the briefest interruption (Figs 191, 192); the longest uninterrupted sequence we have recorded lasted 3 minutes 9 seconds.

Oscillographic analysis shows that nearly all the sound is produced by the closing strokes of the fore wings, although quiet opening hemisyllables are sometimes present. The duration of the two closing hemisyllables comprising each echeme again depends on temperature: 15-25 ms for each hemisyllable is common, but in hot conditions they may last 10 ms or even less and on cool nights tehy may be as long as 50 ms. The second hemisyllable in each echeme is often slightly longer tahn the first. The gap between the two hemisyllables varies from about 6 ms (warm conditions) to about 35 ms (cool conditions), and the interval between successive echemes varies from about 20 ms to about 100 ms, again depending on temperature.

Each closing hemisyllable is typically broken up into a very variable number of discrete pulses of sound separated by gaps of varying duration but usually of theorder of 1 ms. There are sometimes fewer than 10 of these pulses in one hemisyllable (see for example Fig. 204) and so, in such cases, they are unlikely to represent individual tooth-impacts. [1]

References