EXPLOITING THE BIOLOGY OF URBAN MOSQUITOES FOR THEIR CONTROL

Abstract:
The phenomenon of autogeny has been well known in the Culex pipiens complex which consists of several physiological forms. Females of the autogenous form of Cx. pipiens are able to produce the first egg batch without a previous blood meal, whereas anautogenous females need a blood-meal for egg production. Autogeny is genetically determined, however the expression of autogeny is influenced by environmental factors such as larval nutrition, isolation of the breeding site or photoperiod. The autogenous females have to carry over reserves for the production of eggs from the larval stage. The fat body built up by the larva serves the female as source for the yolk production. The condition of food supply for the larvae and the degree of isolation of the breeding site affects the expression of autogeny in the adult. The autogenous form breeds usually below ground in enclosed spaces such as septic tanks and flooded basements in water bodies with a high degree of organic materials. In the northern part of the Palaearctic Region only the autogenous Culex populations bite man and represent the nuisance species. In contrast, the females of the anautogenous variant feed on birds and breed predominantly above ground in unpolluted water. A control strategy against Cx. pipiens should aim solely at the autogenous variant in order to have a target-orientated control operation against the nuisance species. In our study we investigated the biology of the sympatrically occurring variants, the degree of autogeny and finally we developed a monitoring system which enables us to differentiate between both variants. Besides rearing the various populations for proving the autogeny, we studied the genetic differentiation between the two variants by protein electrophoresis. This technique allows a quick identification of the autogenous variants to implement the control.