The effects of three insect growth regulators on egg production in the yellow fever mosquito (Aedes aegypti)

Insect Growth Regulators are a class of insecticides that act not by directly killing the insect, but by disrupting the development of the insect. This class of insecticides is typically applied to larval insects to prevent them from reaching sexual maturity in the adult stage. Frequently this is achieved through ecdysone agonists, which disturb the precise timing of molts, leading to premature lethal molts or inability to molt. Lepidopteran larvae have received the most attention, but some interest has been focused on Diptera as well. More recently, adults are also being studied because of the predominant role that ecdysteroids and Juvenile Hormone play in reproduction. The present study focuses on the effects of three Insect Growth Regulators on vitellogenesis and egg development in the yellow fever mosquito, Aedes aegypti. The insect growth regulators used are the ecdysteroid inhibitor Azadirachtin and the ecdysone agonists Tebufenozide and Methoxyfenozide. The mosquitoes are treated with an IGR in 3 ways; direct injection into the thorax, absorption through the cuticle of the abdomen (facilitated with ethanol), or through ingestion (dissolved in 5% sucrose). The effects of the IGRs are measured with relation to yolk deposition and number of eggs laid. Inhibition of ecdysteroid production is measured by in vitro incubation of ovaries, then analyzed using an ecdysteroid RIA to determine the titer.