330 
Psyche 
[September-December 
the femur against a row of pegs on a longitudinal intercalary vein 
of the tegmen or fore-wing. There are 39 zb 0.88 (S.E.) pegs per 
mm in the file, which averages 6.74 zb 0.17 mm in length. 2 How- 
ever, the mechanism for production of the flutter-rasp still is un- 
known. 
The acoustical properties of the chirp in A. sulphured have been 
illustrated by Otte (1970, p. 22) and the present study confirms his 
report for the usual recording conditions (Fig. 7b). The signal 
rises in frequency from 2 KHz to 6-8 KHz with a duration of 
about 50 msec. The oscillograms also confirm the frequencies re- 
produced in the sonagrams. Even tape recordings made under con- 
ditions for ptenocinematography are only 50 to 75 msec in duration. 
Faint peaks sometimes isolated from the higher amplitude signals 
have been interpreted in the past as sounds made during the upstroke. 
Comparison of Figs. 7 through 48 will show this interpretation 
to be partly correct. However, the entire movement recorded by 
the motion picture camera takes no to 140 msec, during nearly all 
of which time some sound is produced. It is clear that most of the 
sound produced on the upstroke is of such low amplitude and fre- 
quency that it is not reproduced by the audiospectrograph, nor by an 
oscilloscope which is regulated to trigger only on the higher ampli- 
tude sounds. Whether the upstroke is informationally important is 
unknown, but doubtful, since it is so variable in duration. 
The definitive chirp, however, is made on the downstroke. Fig- 
ures 8 through 48 make it clear, from measurements and photographs 
of side and rear views, that the jagged peaked appearance of the 
chirp is not due to pulsed changes in the velocity of movement, for 
the femora move rapidly in a single sweep to the resting position. 
On the other hand, the femora are forced to move in tandem, since 
the pressure necessary to produce the chirp causes the femoro-tibial 
joints to overlap the midline and displace one another. It would 
be interesting to record the first chirps of a young male to determine 
the ontogeny of this metachronous movement. The net result of the 
movement of the two femora is to produce pulses of sonic amplifi- 
cation modulated by irregular low amplitude interference as the 
discrete pulses produced by the two files phase together and then go 
2 The pegs are smaller and more numerous per mm in the anterior 
(proximal) part of the file. The mean — 42.2 ± 0.71 (S.E.) pegs in the 
second mm from the proximal end and 35.8 ± 0.68 in the second mm from 
the distal end of the file. This difference is highly significant statistically 
(t = 6.51, df — 18, p <C<C 0.005, n = 10 animals). Further studies are 
underway to determine the functional significance of this asymmetry. 
