1979] 
Henry — Chrysopa downesi 
293 
terns. The frequency with which the abdomen is jerked or vibrated 
during each volley is quite low and may be modulated (changed) 
during the brief course of the volley. A sexually receptive male and 
female of a given species will establish a duet of abdominal jerking 
during courtship; in such a duet, partners will alternately trade 
volleys, or whole sequences, without overlap or interference. 
I recorded and photographed jerking activity using the equipment 
and techniques of a previous study (Henry, 1979). A ceramic trans¬ 
ducer (crystal phonograph cartridge) picked up substrate vibrations 
produced in a thin plastic membrane by calling lacewings and fed 
these signals to a storage oscilloscope. Conclusions regarding the 
patterns of C. carnea were based on observations of many (more 
than 30) successful courtships performed by numerous pairs of indi¬ 
viduals drawn from populations in Connecticut, New York, Illinois, 
and California; those concerning C. downesi were based on six 
successful and 15 unsuccessful courtships by eleven pairs (7 males 
and 10 females) from the northern Catskill mountains of New York 
State, observed for 69 hours. The source population of C. downesi 
was sympatric with that of C. carnea at the Catskill site. I did not 
find any geographical variation in C. cornea’s calling patterns. 
Results 
Chrysopa cornea’s call (Fig. 1) consists of a long sequence of 40 or 
more short (approximately 1/2 second) volleys of vibration; volleys 
are separated by 1-2 second intervals, and the sequences of two 
insects are interdigitated during duets—i.e., partners alternate vol¬ 
leys (Fig. 1 A). The frequency of abdominal vibration is modulated 
during each volley, from around 100 strokes per second at inception 
to 35 or 40 per second at termination (Fig. IB). Additionally, there 
is a gradual but significant change in the spacing of volleys during 
each solo or duet sequence (Henry, 1979). The calls of this species 
are not markedly sexually dimorphic. 
In contrast, the call of the C. downesi male or female is more 
elaborate than and totally unlike that of C. carnea (Fig. 1C and 
Table 1). A sexually receptive individual will periodically release a 
5-8 second (or longer) sequence of closely-spaced jerking volleys, 
punctuated by a sharp discontinuity where the duration of and 
interval between volleys abruptly change. Part one of each sequence 
consists of four to seven identical (except for gradually increasing 
