Isoperla quinquepunctata CO 1999

Isoperla quinquepunctata.

One hundred seven and seventy-eight signals were obtained from one, 1-day old male and female respectively, at 21°C and normal incandescent lighting. The male and female produced long signals or “symphonies” (Szczytko and Stewart 1979) of repeating 2-way sequences (Range: 2–9), with either the typical female single answer beat following the call (N=69) (Fig. 12A), or with her answer beat(s) interspersed within the 1 st, 3 rd, 4 th, 6 th, 8 th, 11 th, 13 th or 15 th (N=2) male interval (Fig. 12B, first underlined duet). The male called with signals of 7 mode beats; with intervals of 173.6 ± 11.4 ms (Table 3). The average individual call intervals gradually decreased from 179.9 ms (i1) to 171.0 ms (i6), remained fairly uniform until (i15), then increased to 190.8 ms (i20) (Table 4). Mode and mean beats per female signal were 1 and 1.0 ± 0.2; mean beat interval was 924.5 ± 254.0. The ♂ - ♀ exchange interval was 98.0 ± 5.2 ms for sequenced and overlapped duets.

In our analyses, we treated the multiple 2-way sequences and overlapped duets individually, instead of the entire “symphony” (underlined duets, Figs. 12A–B). These duets were separated from one another by consistently longer intervals (279.5 ± 62.4 ms) than typical interbeat call intervals (173.6 ± 11.4 ms).

These results are consistent with Szczytko and Stewart (1979) in terms of general signal description and beats, but differ considerably in beat intervals (Table 5). We propose that our consistently larger overall-mean-interval differences were due to the inconsistencies between their oscilloscope calibration and our computer, explained above under I. phalerata.