The ecology of Psorophora confinnis (Diptera: Culicidae) in southern California. I. The seasonal nature of hatching.

Abstract

The seasonal hatching of the eggs is controlled by the annual cycle of temperature. Preflooding temperatures control the hatchability of the eggs by exerting a conditioning or deconditioning effect. The eggs are conditioned by an increase in temperature and deconditioned by a decrease. All eggs are conditioned when held at 90°F for 1–2 weeks and deconditioned after 4 weeks at 60°. Intermediate temperatures may either condition or decondition the eggs, depending upon the previous temperature of exposure, since conditioning occurs only at temperatures higher than the prior deconditioning temperature. Thus, temperatures of 70° and 80° condition eggs in late spring and early summer, and decondition eggs in late summer and early autumn. The percentage of conditioned eggs that hatch when flooded varies directly with the temperature of the medium. The combined effects of preflooding and flooding temperatures upon the hatching of the eggs control the seasonal occurrence of adults. Deconditioned eggs do not hatch during the winter, although repeatedly flooded by irrigation water.