Abstract
Cross-breeding experiments between molestus (autogenous) and pallens (anautogenous) strains of Culex pipiens sensu latu were carried out by using genetic markers Gr (green larva) or Or (orange larva) in colonies established from naturally occurring mutants as the weaus for investigating their copulation habits. 1. In the crosses between Or-females and Ormales plus Gr-males, 13% of the egg rafts produced larvae showing mixture of the two different colour characteristics of Or and Mix, which indicated that their mothers were inseminated by at least two males with different genetic markers. This fact suggests that females of Culex pipiens s. l. can copulate with two or more males and their offspring from the same egg raft may have different fathers. 2. In the crosses of pallens-females with Gr-males plus pallens-males in the same cages or of Gr-females with Gr-males and pallens-males, it was also demonstrated through hatchability of egg rafts and by larval colour characters that pallens or Gr females sometimes copulate with both pallens and Gr males, and can produce mixed larval colonies with different fathers. 3. In the mixed crosses of Gr-females plus pallens-females and Gr-males plus pallens-males, 6.3% of egg rafts deposited by pallens-females were composed of a mixture of eggs inseminated by both pallens and Gr males. 4. In the mixed crossing experiments between males and females or different forms belonging to the same age groups, selection in copulation between the same forms were observed. However, in the mixed crosses of same and different forms copulated with males of different ages, i. e. those emerged one and eight days before, the females were found to more frequently copulate with younger males, irrespective of the form to which this belonged.
