Ovarian diapause in three geographic strains of Culex pipiens (Diptera: Culicidae).

Abstract

Ovarian diapause and blood feeding by 8- to 12- day-old mosquitoes reared under several photoperiods were compared among the following Culex pipiens populations: Cx. p. quinquefasciatus from Houston, Texas; Cx. p. pipiens from Fort Collins, Colorado; a genetically mixed strain from Memphis, Tennessee; and Houston × Fort Collins hybrids. The Houston mosquitoes (except for 2 of 141) did not enter diapause, even under a 7-h photophase. The Fort Collins strain showed complete diapause with 9 h of light but no diapause with 15 h. Response by the Memphis mosquitoes was intermediate between those of the Houston and Fort Collins strains. Diapause incidence in crosses and backcrosses involving the Houston and Fort Collins stocks correlated negatively with the proportion of their genomes contributed to the various hybrids by the Houston strain. Blood feeding was inhibited by short photophases in the Fort Collins mosquitoes but was largely independent of photoperiod in the Houston and Memphis strains. In nature, the diverse proportions of Cx. p. quinquefasciatus genes carried by hybrid females can be expected to prevent many from entering diapause, extending their potential as St. Louis encephalitis vectors but making their winter survival unlikely.