OVIPOSITION ATTRACTION AND REPELLENCY OF AEDES-AEGYPTI (DIPTERA, CULICIDAE) TO WATERS FROM CONSPECIFIC LARVAE SUBJECTED TO CROWDING, CONFINEMENT, STARVATION, OR INFECTION

As the biomass of Aedes aegypti (L.) lan;ae increased in relation to t he volume of rearing waters, oviposition attraction of these waters to conspecific, gravid females first rose to a peak and then declined. F urther increases in biomass rendered waters strongly repellent. Compar able responses were elicited by a decrease in the volume of rearing wa ters or an increase in the relative size or number of mosquito larvae. Low volumes of water reduced oviposition attraction and increased rep ellency, whereas larger volumes increased attraction. Excessively larg e volumes diluted attraction to neutrality. Constraints imposed by the physical dimensions of the larval environment which interfered with t he normal postural movements and behaviors of the larvae also induced repellency, independent of rearing volume. Titration of repellent wate rs revealed that infection with the digenean Plagiorchis elegans (Rudo lphi) generated the most powerful repellent effect, whereas crowding o r starvation induced significantly weaker responses. At no time did di lution of repellent waters restore attractive properties. Repellents, even at minute concentrations, overrode attractants. The density-depen dent action of oviposition attractants and repellents may help to main tain larval populations near optimal levels through their influence on recruitment. Oviposition repellency induced by sublethal infections w ith P. elegans may maintain population levels below the carrying capac ity of the environment. Persistence of oviposition attraction and repe llency varied inversely with temperature. The magnitude of the repelle nt effect induced by larvae appears to he a good indicator of their pr obability of survival and may be of selective significance. Repellency may deflect ovipositing females away from sites close to human habita tion and may lead to new, and perhaps more effective, method, to contr ol mosquitoes and the diseases they transmit.