Superparasitism of the Caribbean Fruit Fly, Anastrepha suspensa (Diptera: Tephritidae), by Biosteres longicaudatus (Hymenoptera: Braconidae): Implications for Host Regulation

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Abstract
Some solitary and gregarious (one and several individuals, respectively, per host) parasitic insects regulate their hosts by inducing changes in host development, behavior, and morphology. However, preliminary evidence suggested that single parasitizations by the solitary wasp Biosteres longicaudatus Ashmead do not significantly alter development of the host Anastrepha suspensa (Loew). Therefore, A. suspensa larvae and prepupae containing 1-3 (Group A), 4-6 (Group B), and more than 8 (Group C) B. longicaudatus first instars were studied to evaluate the impact of parasite load on wandering behavior, onset of pupariation, larval/pupal apolysis, and size and weight of the host. Upon initiation of wandering behavior, individuals in Group C traveled a significantly shorter distance in 1 h than those in Groups A, B, or the control. Average time from onset of wandering to pupariation was 5.5, 5.1, 4.3, and 3.0 h for the control and Groups A, B, and C, respectively. Larval/pupal apolysis was initiated on day 2 of pupariation in all except Group C, which apolysed between day 3 and day 4 of pupariation. The puparia in Group C weighed significantly less than those in the other groups because of rapid depletion of host tissues by as many as 15 parasite first instars per host. “Cigar-shaped” puparia constituted 4.4% of Group A, 6.6% each of Group B and the control, and 23% of Group C hosts. The above results suggest that, in some cases, host developmental alterations induced only under conditions of superparasitism by certain solitary parasites like B. longicaudatus and characterized as host regulation may instead be artifacts of superparasitism.

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