The absence of host-seeking behavior during the first gonotrophic cycle in Aedes atropalpus is not due to hemolymph-borne factors. The removal of all developing eggs from nulliparous, gravid individuals by ovariectomy did not result in host-seeking. Furthermore, hemolymph transfers from non-host-seeking, nulliparous, gravid females into host-seeking, parous, non-gravid females did not inhibit host-seeking in the recipients. Circumstantial evidence supports the hypothesis that distention inhibits host-seeking during the first gonotrophic cycle in this species. Host-seeking can only be elicited after oviposition of the first egg clutch. Although the frequency of sugar feeding is high, particularly in the parous, non-gravid population, host-seeking is not correlated with the presence of sugar in the crop. Host-seeking and non-host-seeking individuals were equally likely to have recently fed on sugar. The control of host-seeking behavior during the first gonotrophic cycle in Ae. atropalpus is thus very different from that in the anautogenous mosquito Aedes aegypti, in which host-seeking is inhibited by hemolymph-borne factors associated with egg development.