none Callosobruchus chinensis; Dinarmus basalis; Anisopteromalus calandrae; Heterospilus prosopidis; We investigated the control of the sex ratio in three ectoparasitic solitary wasp species, Dinarmus basalis (Rondani), Anisopteromalus calandrae (Howard), and Heterospilus prosopidis Vier., parasitizing azuki bean weevil (Callosobruchus chinensis (L) (Coleoptera: Bruchidae)) larvae. By either artificially transferring wasp eggs onto larger hosts, or letting eggs develop on the hosts on which these were laid, we measured the primary and emergence sex ratios of offspring wasps on different aged hosts. In all species, sex ratios from older hosts were more female biased. However, there was significant differential mortality between sex during the larval stage, especially on younger hosts. Further experiments showed that wasps did not lay more female eggs on larger hosts of the same age, suggesting that offspring sex was not controlled by the individual size of the host on which a female oviposited.