Development of the parasitoid Psyttalia humilis (Sylvestri) on Anastrepha suspensa (Loew), a New World tephritid fruit fly host

Many hymenopteran parasitoids are effective biological control agents against insect pests. The larval-pupal parasitoid Psyttalia humilis (Sylvestri) (Hymenoptera: Braconidae) successfully suppressed populations of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in Hawaii in the 1930s. Little is known about P. humilis as a parasitoid of New World fruit flies or of its development in these hosts, though such knowledge could be useful in efforts to identify new parasitoids to control species of Anastrepha, particularly the Caribbean fruit fly, A. suspensa (Loew) (Diptera: Tephritidae). The objectives of this study were to determine (1) the age-related biotic potential of P. humilis females, in order to identify an optimal age for parasitizing A. suspensa larvae, (2) the fecundity of females, and (3) the number and duration of the immature stages of P. humilis within A. suspensa. Adult females were housed with males from 0 to 7 days after emergence and daily dissections of their ovaries revealed that the number of chorionated eggs (biotic potential) increased from 30 in 0 day-old females to 73.5 eggs 2 days later, then declined to 48.5 at 7 days post emergence. Sequential dissections of hosts, parasitized for 3 h at a 1:20 parasitoid:host (early 3rd instar) ratio, revealed that females oviposited 0-3 eggs/host. The egg stage and first larval stadium lasted 2-3 and 2-3 days, respectively. The remaining larval instars and their duration need to be clarified. Studies are in progress to determine optimal parameters for mass rearing this parasitoid.