The Influence of the Apical Droplet of Culex Egg Rafts on Oviposition of Culex Pipiens Faticans (Diptera: Culicidae)

Abstract

Culex pipiens fatigans females were offered a choice of oviposition sites, and a significant response was recorded to the presence of egg rafts at various densities. Further experiments indicated that this response was due to the presence of the apical droplet material located on each egg. A larger amount of apical droplet material produced a more highly significant response. The attractant properties associated with the apical droplets decreased with time. Cx. p. fatigans responded in an idenical manner to 1 egg raft of Cx. p. fatigans, Cx. p. molestus or Cx. tarsalis, thus establishing the nonspecific nature of the attractant. Cx. tarsalis required the presence of larger numbers of egg rafts before showing a response. The male mosquito played no role in the formation of the apical droplet or its attractant properties. Simulated egg rafts were not attractive. Oviposition by Cx. p. fatigans was not influenced by the presence of larvae or pupae at 2 different densities, by the presence of trapped adults at the water surface or by a 5% sucrose solution.