As done previously with adult females of Culex pipiens pallens Coquillett, a mixture of 17 amino acids was infused into the hemocoel of females of seven anautogenous and one autogenous mosquito species belonging to three genera. In Culex. p. quinquefasciatus Say, Cx. tritaeniorhynchus Giles, Cx. kyotoensis Yamaguti & LaCasse, Aedes albopictus (Skuse), Armigeres subalbatus (Coquillett), and Cx. p. molestus Forskal, which previously had laid autogenously matured first batch of eggs, ovarian development was stimulated and frequently continued to maturity. In most mosquitoes, the number of mature follicles nearly doubled when the period of infusion was extended from 24 to 48 h. Therefore, the two previously indicated roles of amino acids, one to initiate ovarian development and the other to regulate the number of maturing oocytes, were confirmed in these species. In Cx. halifaxii Theobald and Ae. japonicus (Theobald), however, the frequency of activation and maturation of ovaries was low compared with the other species, indicating that those species may require some factors other than an increase in amino acids for normal ovarian development after a blood meal.