Effects of diurnal thermoperiods and quickly oscillating temperatures on the development and reproduction of crickets, Gryllus bimaculatus

Abstract

1. Embryonic development, larval growth and fecundity of Mediterranean field crickets, Gryllus bimaculatus, were determined at various constant, daily alternating and quickly oscillating temperature regimes. 2. At constant temperatures ranging from 20° to 34° C embryonic development follows the rule of sum of hourdegrees above zero point. In variable temperature regimes some acceleration in the rate of egg development is present. However, compared with mean constant temperatures a higher amount of hour-degrees is necessary to complete egg development. 3. No larval development was possible at constant 20° C, whereas complete larval development is observed at diurnally alternating LTD conditions, corresponding to a mean constant temperature of 20° C. Quickly changing temperatures, oscillating around the same mean value of 20° C, further accelerate larval development. 4. Females housed at 26°:14° C/2:2 h, 7:7 h or 8:8 h produced higher numbers of eggs than those at any of the constant temperature regimes. 5. The decision as to which temperature regime is the most favorable for the development, reproduction, and survival of G. bimaculatus is based on the net reproduction oer generation (R _o) and the capacity for increase (r _c).A maximum in R _o is observed in the 2:2 h temperature regime, whereas the capacity for increase is maximal at constant 27° to 34° C. 6. The probable mechanisms for increased rates of development and reproduction under variable temperature regimes and the ecological significance of the results are discussed.