Bi-autogenous ovarian cycles in Egyptian Aedes caspius Pallas (Diptera:Culicidae).

Autogenous Aedes (Ochlerotatus) caspius Pallas from Aswan deposits 1 to 2 egg batches without a blood meal. Repeated ovarian developmental cycles were responsible for the bi-ovipositional pattern as indicated by the presence of 2 dilatations in the ovariolar pedicel of bi-autogenous females and by the early stages of development of the ovaries (II and II B) observed 1-3 days following initial oviposition, later stages of maturation occurred progressively. Three levels of autogeny were distinguished within the population: mono-autogenous females that deposited 1 egg batch and were unable to initiate further oogenesis (54.4%), mono-autogenous females in which various degrees of vitellogenesis developed posterior to initial sole oviposition (40%) and bi-autogenous females (5.6%) that deposited 2 autogenous egg batches but were unable to develop any further oogenesis. The fecundity of mono-autogenous females (about 56 eggs) whether they could develop a 2nd autogenous cycle or not, was comparable to that of bi-autogenous mosquitoes in their initial egg batch (53 eggs), suggesting that ability to develop a subsequent autogenous follicular cycle is determined by factors independent of nutrient reserves accumulated during the larval stage. The 2nd egg batch of bi-autogenous females was smaller (21 eggs) than the initial batch. The total reproductive effort of bi-autogenous individuals (about 74 eggs) was superior to that of mono-autogenous females. However, bi-autogenous females laid the totality of their eggs within about 16 days, whereas the average initial gonotrophic cycle of mono-autogenous females was 6 days. It is concluded that bi-autogeny in Ae. caspius would be of little value in the population increase although it may contribute maintaining the species when the host is not available.