Factors Influencing Oviposition in Aedes Triseriatus (Diptera: Culicidae)

Abstract

JeffreylBeehler'-3, Sharor^Lohr2 and GenejDeFoiiart' ABSTRACT Five factors associated with natural oviposition sites tested for their attractancy to ovipositing Aedes triseriatus, including dyed oviposition water, presence of decaying organic matter, dark oviposition container, water in which conspecific larvae have been reared to the 4th instar and the presence of eggs the balsa wood oviposition substrate. A replicated frac-tional factorial design used to the effects of the above factors oviposition behavior in laboratory experiments. Regression analysis showed dyed oviposition water and eggs the oviposition substrate to be statisti-cally significant afctractants for ovipositing A. triseriatus females. The attrac-tion to dyed oviposition water indicated that dyed water in oviposition traps may greatly increase their eompetiveness with naturally occuring oviposition sites-Aedes triseriatus (Say) is woodland mosquito in the upper midwestern United States. It breeds primarily in treeholes, although other containers such discarded fcires may also be used oviposition sites. This species is the vector of La Crosse encephalitis virus (DeFoliart et al. 1986) and thus, there is much interest in monitoring its presence. Unfortunately, A. triseriatus responds poorly to light traps (Craig 1983), and since it breeds in containers, it is not subject to sampling by dipper. To detect its presence, Loor and DeFoliart (1969) adapted the ovitrap previously used for monitoring Aedes aegypti (Linn.) during the Pan American Health Organization A. aegy-pti eradication program. The trap consists of water-filled, black-painted, 400 ml beverage containing balsa paddle (Novak and Peloquin 1981) which artificial oviposition site, A number of physical and biological factors have been suggested ovipo-sition attractants for Aedes triseriatus. Physical factors which influence A. triseriatus oviposition include the orientation of the opening of the oviposition container, texture and coloring of the container walls, and the optical density of the oviposition water (Wilton 1968), Novak and Peloquin (1981) used dark oviposition containers when determining if egg counts differed in relation to the oviposition substrate provided in the ovitrap. They found balsa substrates to be best suited for A biological factor reported oviposition attractant for A. triseriatus is the presence of decaying organic matter in the oviposition water (Wilton THE GREAT LAKES ENTOMOLOGIST 1968) Decaying organic matter has often been reported oviposifcion attractant with other Aedes and Culex species (e.g. Kramer and Mulla 1979. Hazard et al. 1967). Hazard et al. (1967) also found that the volatiles produced from the bacteria associated with organic infusions induced oviposition Ess pheromones have been reported oviposition afctractanfcs Culex tarsalis^Coquillett and Culexpipiens (Linn.) (Osgood 1971, Dadd and Khenjan 1974). These volatiles induce oviposition when eggs of conspecifics present. Another volatile attractant is the larval factor (LF), which pro-duced by 4th instar conspecifics and is present in larval holding water. Bentley et al. (1976) showed that LF present in the holding water of 4th instar A. triseriatus. The LF also shown to be present in the volatile fraction of holding water. By treating water with kaolin, McDaniel et al. (1979) showed that LF not associated with waste products larval gut bacteria.