Action de la température sur le développement embryonnaire de Libellula julia Uhler (Anisoptera: Libellulidae)

Eggs of L. Julia were submitted to different constant-temperature regimes (10-35° C) under a constant photoperiod of 16 hr of light. The hatching threshold is 12.5°C, and the lower threshold of development according to R.T. TROTTIER’s formula (1971, Can. Em. 103: 1671-1683) is 11.76° C. Temperature range of development is between 20° and 30° C, with an optimum at 25° C (mean hatching time of 7.76 days). Different mathematical formulations of the velocity curve are compared. J. DAVIDSON’S sigmoid curve (1944, J. Anim. Ecol. 13; 26-38) corresponds closely with the observed development.