Basic biology and small-scale, rearing of Celatoria compressa (Diptera : Tachinidae), a parasitoid of Diabrotica virgifera virgifera (Coleoptera : Chrysomelidae)

The tachinid Celatoria compressa Wulp has been evaluated as a candidate biological control agent for the western corn rootworm, Diabrotica virgifera virgifera LeConte, in Europe, where it is an invasive alien pest of maize. Special emphasis has been placed on understanding aspects of the parasitoid basic biology and on developing a rearing technique for a small-scale production of C. compressa puparia. The age of C. compressa adults was found to be the most crucial factor in achieving mating. Only newly emerged, 1-h-old females, mated successfully with 2- to 5-day-old males, achieving a success rate of 74%. After mating, a prelarviposition period of 4 days occurred. The 5-day-old C. compressa females inserted their eggs containing fully-developed first instars directly into adults of D. v. virgifera. Total larval and pupal developmental time, including a pre-larviposition period of 4 days, was 29 days under quarantine laboratory conditions (25 C daytime, 15 C at night, LID 14:10, 50% +/- 10% r.h). Females of C. compressa were capable of producing on average 30 puparia throughout a female's mean larviposition period of 15 days. A large number of host attacks by C. compressa were unsuccessful, resulting in a mean larviposition success rate of 24% per female. Parasitoid females appear to have difficulties inserting the egg through the intersegmental sutures or membranes around leg openings of the host adults. Although the. small-scale rearing technique of C. compressa presented is both time and labour intensive, C. compressa has been reared successfully for at least 20 successive generations without shifting the 1 male: 1 female sex ratio using a non-diapause strain of D. v. virgifera.