Effects of ambient temperature, humidity, and age on wing-beat frequency of Periplaneta species

Abstract

Wing-beat frequency of 2-week-old male Periplaneta americana cockroaches was measured during tethered flight at ambient temperatures from 19 to 35°C and 50 and 95% r.h. Between 19 and 27°C the frequency increased at a nearly constant rate (0·6 Hz/deg at 50% r.h.; 0·7 Hz/deg at 95% r.h.), but the rate of increase decreased markedly between 27 and 35°C. This decline differed from results of past investigations of wing-beat frequency for this species. Wing-beat frequencies at 95% r.h. were significantly higher than those at 50% r.h. for ambient temperatures between 27 and 35°C. reductions in wing-beat frequency at high temperatures and differences in wing-beat frequency between 50 and 95% r.h. may reflect decreases in internal thoracic temperature resulting from cuticular water loss. P. americana females lack the capacity for sustained free flight, but were tested in tethered flight in the same manner as males. Wing-beating lasted only 3 to 8 sec compared to 5 to 6 min for males. However, wing-beat frequency did not differ significantly from males except at one temperature and humidity combination, 35°C and 95% r.h. Failure of females to sustain wing-beating may be due to the lack of available energy in the flight muscles. Wing-beat frequencies among 2-week-old P. australasiae, P. brunnea, and P. fuliginosa males in tethered flight at 19 to 35°C and 50% r.h. were similar to P. americana males. P. australasiae differed significantly from P. brunnea over the entire range of temperatures, but only minor differences occurred among the other species. As they matured, males of the four species showed similar changes in wing-beat frequency at 25°C, 50% r.h., and only small consistent differences between species occurred. Wing-beat frequency could not be determined 1 to 3 days after eclosion because no wing beating occurred. On days 4 to 6 the frequency was approximately the same for all species, 23 Hz. Frequency increased to approximately 26·5 Hz on day 7 and by day 14 reached a maximum level of 30 to 31 Hz which was maintained until the termination of the experiment on day 35.