Studies on autogeny in natural populations of Culex pipiens. 3. Midsummer preparation for hibernation in anautogenous populations.

Abstract

In a local population of Culex pipiens in Boston, ovarian diapause was studied with reference to the condition of presumptive ovarian follicles; the presence of follicular relics, stored sperm, and hypertrophic fat; and readiness to feed. Anautogenous C. pipiens first entered ovarian diapause Boston during the 2nd week of August, somewhat after the larval population began to decline. Two weeks later, the first mosquitoes with enlarged fat bodies appeared. During September such fat mosquitoes did not feed upon blood, but thereafter became hematophagous. Ovarian diapause was disrupted during October. Thus, ovarian diapause appears to be a transient condition that precedes hypertrophy of the fat body. Diapause-stage follicles apical to follicular relics were common throughout August and thereafter. However an anomolous seasonal distribution suggests that this finding is not an indication of hibernation by parous mosquitoes.