1969] 
Willey and Willey ■ — Social Displays 
285 
The flight crepitation. 
The spontaneous aerial crepitation is a buzzing flight, which lasts 
one to three seconds, during which the grasshopper describes an arc 
one to ten feet in length and three feet in height. Males make more 
crepitation flights, by far, than females, which seldom are seen in 
flight except during the first weeks of the season. The flights by 
males may be repeated in a minute, but they average only one such 
sequence every three to four minutes at the peak of daily activity 
during the most active part of the short adult season. Even if 
disturbed, these insects usually crepitate normally. Only when dis- 
turbed a second time will they fly away relatively soundlessly. 
Crepitation flights are usually into the wind if there is only a slight 
breeze, although such flights are suppressed entirely by wind above 
IO m.p.h. On the other hand, silent escape flights are usually at least 
30 feet in length and often extend over several hundred feet, flying 
with the wind (Willey & Willey, 1967). 
The sound produced by the wings during crepitation is shown 
in Figure 2. Each pulse is a broad spectrum click with no distinct 
fundamental frequency nor apparent harmonic. The highest ampli- 
tudes are in a range from 3000 to 8000 Hz and the total range of 
the sound is restricted by the effective frequency response of the 
recording system (20 to 18,000 Hz). To the human ear it is tone- 
less and sharp. There are about 45 pulses per second and they are 
evenly spaced unless a change of direction or landing occurs. At 
these times the pulses take on an added component, appearing double, 
and are more closely spaced. These changes are probably due to 
the wings beating faster and out of phase with one another. 
Male-female interaction (courtship and copulation). 
The chirp is the primary sound generated by the male during 
courtship. This sound is produced by rubbing a ridge on the medial 
side of the hind femur on a linear series of pegs situated in both 
sexes on a modified intercalary vein of the tegmen. The chirp is a 
unitary sound probably produced by an intense pressure of the femur 
on the tegmen in a smooth up and down stroke cycle. As can be 
Figure 2. Field recording of beginning and ending of flight crepitation. 
This flight began 3 feet from the microphone, described a long arc to 10 
feet away and returned to the same spot. Note the increased pulse rate 
(= wing beat frequncy) as the insect gains altitude. The pulse rate in 
mid-flight is more regular. Also note the double wave fronts as the insect 
lands, probably representing wings beating out of phase with one another. 
The break in the middle of the display — 1.8 seconds. 
Figure 3. Audiospectrogram of Exakta camera re-set sounds. 
