Influence of Cohort Age and Host Age on Oviposition Activity and Offspring Sex Ratio of Biosteres tryoni (Hymenoptera: Braconidae), a Larval Parasitoid of Ceratitis capitata (Diptera: Tephritidae)

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Abstract
Factors important in oviposition activity of the parasitoid Biosteres tryoni (Cameron) were examined using the Mediterranean fruit fly,Ceratitis capitata (Wiedemann), as a host. B. tryoni females preferentially oviposited into larvae of middle and late third instars compared with early third instars. The ratio of female parasitoid progeny ranged from < 42% from early third host instars to > 60% of late third instars particularly at early parasitoid ages of 1-8 d. However, the proportion of uneclosed parasitized host pupae increased to a maximum of 34.4% for late third instars. The proportion of ovipositing parasitoid females in a cohort increased progressively (to 35.6% maximum) with parasitoid female age. Maximum average yield of parasitoids per oviposition unit (modified Petri dish with a tight-fitted lid) was 230.8, 210.2 and 199.6 for late third, mid-third, and early third instar hosts, respectively. Yields of parasitoid age groups from 5-16 d were optimum.