Sexual Behavior of Mosquitoes. 1. Age Dependence of Copulation and Insemination in the Culex pipiens Complex and Aedes taeniorhynchus1 in the Laboratory

Abstract

Tethered Culex pipiens pipiens L., C. p. quinquefasciatus Say, or Aedes taeniorhynchus (Wiedemann) (Diptera: Culicidae) females of known age were flown among males during an artificial sunset. Dissections showed that, despite repeated genital contact during pairing, females were not inseminated unless, after pairing, the male first disengaged his legs and hung briefly from the female in an end-to-end position with their genitalia interlocked. This behavior became the criterion for copulation because it was the only behavior which resulted in insemination. Many young tethered females were unreceptive to copulation, and many of those which copulated were refractory to insemination. As the age of the females increased, both receptivity and the rate of insemination increased. Similarly, when females were caged with older males for 22 hours through a single sunset-sunrise, the insemination rate increased with increasing age of the females. Under these conditions, C. p. pipiens and C. p. quinquefasciatus females were not inseminated until they were more than 24 hours old at sunset, whereas most C. p. molestus Forskal were inseminated if they were 6 hours old at sunset. This difference is another important one between the autogenous and anautogenous forms of the C. pipiens complex. Reports of “mating” in male swarms generally imply insemination of the female, although many of the observations may have been of mosquitoes pairing rather than copulating. Because receptivity to copulation and responsiveness to insemination are dependent on the age of the female, the assumption that mosquitoes copulate and are inseminated in male swarms should be tested experimentally.