Conocephalus (Anisoptera) dorsalis (Latreille, 1804)

The male calling song, produced mainly during the daytime, consists of long bursts (lasting up to 2 minutes or more) of a faint sound made up of two alternating components following each other without pause. One component is an echeme-sequence with a rustling quality, composed of tetrasyllabic echemes repatead at the rate of about 11-17/s; the other is a rapid ticking sound composed of single syllables repeated at the rate of about 15-30/s, with the repetion rate often becoming slower during the period of ticking. Each echeme-sequence usually lasts between 2 and 10 s, but longer sequences of up to 30 s or more occassionally occur. The periods of ticking are on average shorter, usually lasting between 1 and 5s, but there are occassionally longer bursts (up to 20 s or more), especially at the beginning or end of a period of continuous singing.

Oscillographic analysis shows that each echeme of the rustling component of the song consists of four very similar diplosyllables (in contrast to the less uniform trisyllabic echemes of C. discolor). The first opening hemisyllable and the last closing hemisyllable of each echeme are usually slightly longer than the interveningones, each of which lasta about 10-13 ms. Within each echeme the intervals between successive syllables are about 2-3 ms and the whole echeme lasts about 50-65 ms; successive echemes are separated by an interval of about 6-15 ms.

The ticking component of the song is composed of diplosyllables very similar to those forming the ticking components of the song of C. discolor. [1]

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