Tettigonia viridissima

behaviour · bio.acousti.ca

The great green bush-cricket is nocturnal, but the males often sing from mid-afternoon onwards. The song is one of the loudest emitted by any British orthopteran, and cen be heard at distances of several meters (Ragge, 1965, says 200 metres, but this is presumably for those with better hearing than mine!). The tone is slightly metallic and rasping, and is produced in continuous, prolonged bursts. When singing the male appears to 'pump' his abdomen rhythmically - presumably to anhance respiration. Even when singing the crypti ccoloration of a male perched among vegetation makes it very difficult to locate. There is some competition between males for song perches, and where the population is dense one may nip an intruder with his mandibles. The latter will usually dive down into lower vegetation.

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behaviour · bio.acousti.ca

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.

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behaviour · bio.acousti.ca

The song is a loud buzzing audible from about 50m. As two syllables are coupled into a double sound, the song - in contrast to T. cantans - is always clearly cut up into 'pulses' of sound.

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behaviour · bio.acousti.ca

Lehtohepokatilla on kovaäänien kutsulaulu, joka voi kuulua jopa yli sadan metrin päähän. Laji aloittaa laulunsa yleensä iltapäivälla, ja mikäli lämpötila on riittävä, laulu on kiihkeimmillään illalla ja se jatkuu heikentyneenä aamuun asti. Sirittääkseen lehtohepokatti vaattii noin kymmenen asteen tai heiman korkeamman lämpötilan. Kutsulaulu jatkuu lämpimällä ilmalla pitkään ilman taukoja (CD2, CD3), mutta lämpötilan laskiessa se muuttuu katkonaiseksi (CD27). Soiton alkaessa iltapäivällä tai lämpimänä päivänä jo aamupäivän puolella se on aluksi katkonaista. Äänen voimakkuuden huippu on noin 10 kHz:n taajuudessa (kuva s. 34).

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