1983] 
Henry — Chrysoperla plorabunda 
349 
other very little, at any temperature, in any major characteristics of 
their calls. Particularly coincident between males and females are 
the initial volley frequencies and the volley durations (Table 1 and 
Fig. 2A and E) of Ch. plorabunda calls. There is a consistent ten- 
dency for females to vibrate their abdomens in later portions of their 
volleys at somewhat lower frequencies than do males (35 cycles/ sec. 
vs. nearly 40 cps at 20°C; see Fig. 2C) and for volleys to be produced 
rather more slowly by males than by females (about 66 volleys/ min 
vs. nearly 70/ min at 29.5°C; same figure, D), but neither of these 
differences is statistically significant. 
Secondly, it can be seen from Figures 2 and 3 that the slopes for 
the linear regressions of frequency versus temperature differ radi- 
cally from one portion of a volley to another, gradually becoming 
less steep as the volley progresses. Thus, initial portions of volleys 
change frequency rapidly with temperature (slope = 4.27x; Fig. 3A), 
while terminal portions remain within a much narrower range of 
values over equivalent temperature extremes (slope = 0.960x). X- 
intercepts also differ significantly for each of the three regressions 
calculated from pooled frequency data on all ten individuals: inter- 
cepts of 3.60, —1.27, and — 19.09°C respectively characterize initial, 
median, and terminal portions of volleys. Regression of another call 
parameter, volley repetition rate, against temperature produces a 
line with a slope of 3.25x and an X-intercept of 9.14°C (Fig. 3D). 
Thirdly, Figure 3E demonstrates that volley duration decreases 
markedly with increasing ambient temperature, and that the mathe- 
matical relationship between the two can equally well be interpreted 
as linear or exponential. In theory, the total number of abdominal 
strokes per volley could remain constant as temperature varies, 
since the increased frequency of abdominal vibration at higher tem- 
peratures would automatically shorten volley duration. However, 
data in Table 1 suggest that higher temperatures induce a slight but 
significant reduction in the total number of abdominal strokes pro- 
duced during each volley, and that this phenomenon facilitates the 
volley-shortening process. 
Finally, the table and figures all support the view that deviation is 
relatively slight between the temperature data for each of the var- 
ious call parameters and the linear regressions calculated from those 
data. The closest fit to a mathematical relationship is found in the 
initial frequency of abdominal vibration during a volley: for data 
