Thermal effects on embryonic development in four summer species of Libellulidae (Anisoptera)

More than 32,000 fertilized eggs from Erythemis simplicicollis (Say), Libellula cyanea Fabr., L. incesta Hag. and Perithemis tenera (Say) were maintained at several regimes until eclosion. Between 20-35°C, development was progressively faster at each higher temperature; at this thermal range incidences of successful eclosions were also highest. At 15°C hatching was either greatly delayed or prevented, and at 40°C, no eclosions were noted; these temperatures mark the approximate lower and upper thermal thresholds for eclosion in these spp. Hatching peaks occurred during the first 1-3 days of the eclosion period. Numbers of eggs per clutch varied widely within and between spp.; clutch sizes ranged from a mean of620 for E. simplicicollis to 1366 for L. cvanea.