1983] 
Henry — Chrysoperla plorabunda 
357 
30-40% in the calls of their bugs and small cicadas, lacewings of the 
species Ch. plorabunda alter their rate of abdominal vibration by 
50-60% during each volley, suggesting that their calls can propagate 
efficiently and evenly through a variety of substrate types. However, 
if all this is true, it remains to be explained why other lacewing 
species like Ch. dow nesi and Ch. carnea (central Europe) produce 
long calls of nearly constant frequency characteristics (Henry 1980b, 
1983a). Perhaps specific properties of the typical substrates utilized 
by those species have shaped and narrowed the frequency ranges of 
their calls over evolutionary time: for example, Ch. downesi may be 
responding to some inherent acoustical property of conifer needles, 
since its ecological niche is restricted to the evergreen forests of 
North America. 
Summary 
This study assesses the effects of temperature on the major 
characteristics of the vibrational song of a North American green 
lacewing, Chrysoperla plorabunda (formerly Ch. carnea). Those 
parameters include the volley repetition rate, the average duration 
of volleys, the total number of abdominal strokes per volley, and the 
vibrational frequency structure of volleys. In general, temperature 
affects the call in a direct linear manner, so that linear regression 
equations (of differing slopes) can be used with confidence to des- 
cribe the relationship between temperature and each measurable 
trait of a lacewing’s song. Additionally, variation in these equations 
among individuals or between the sexes is negligible, so all members 
of the species produce calls of remarkably similar construction at all 
reasonable ambient temperatures — a prerequisite to unambiguous 
communication among conspecifics. That the weight of an in- 
dividual’s abdomen has no effect on the frequency characteristics of 
its call was demonstrated experimentally by mass-loading the 
abdomens of several sexually receptive insects. The relevance of 
these findings to the biological function of lacewing calling, as well as 
to the physics of substrate-borne vibrations, is discussed briefly. 
Acknowledgments 
This study was supported in part by National Science Foundation 
award #DEB-79-l 1537 to the author. I thank Dr. James Johnson, 
University of Idaho (Moscow), for sending me living Chrysoperla 
