ABSTRACT.The ecdysteroid titre of adult females resulting from a cross ofAedes epactiusfemales, an anautogenous mosquito, withAedes atropalpusmales (an autogenous strain) was determined using a radioimmunoassay. The F1hybrid is autogenous and produces mature oocytes without the benefit of a blood‐meal. The ecdysteroid profile of this hybrid revealed a smaller early peak and a second larger one. Qualitatively the overall hormonal profile appeared quite similar to the ones previously obtained usingA.atropalpusfemales and blood‐fedA.aegypti.Quantitatively, the amount of endogenous hormone exhibited, and the total number of mature oocytes produced, may be positively correla