Notes on the biology and ecology of the parasitoids of the poplar clearwing moth, Paranthrene tabaniformis (Rott.) (Lep., Sesiidae) in Bulgaria. I. Apanteles evonymellae (Bouché, 1834) (Hym., Braconidae)

Aspects of the biology and ecology of Apanteles evonymellae (Bouché), a parasitoid of the poplar clearwing moth, Paranthrene tabaniformis (Rott.), were studied during the period 1987–96. One-year-old poplar ( Populus spp.) shoots infested with P. tabaniformis larvae were collected during the winter months at 11 localities in Bulgaria and examined in the field and laboratory. Apanteles evonymellae was recorded in all areas studied in Bulgaria. The mortality of P. tabaniformis caused by this parasitoid in various regions of Bulgaria varied from 2.4 to 35.4%; the average for the country was 17.3%. Laboratory observations showed that A. evonymellae is a solitary endoparasitoid of the poplar clearwing moth. It develops in early-stage (first- to fourth-instar) host larvae and overwinters as a larva in the host. Apanteles evonymellae is bivoltine, but only the second generation is associated with P. tabaniformis . In the field, adult parasitoids of first generation appear in April about 1 month before the emergence of P. tabaniformis . The longevity of A. evonymellae adults is a maximum of 6 days. Therefore, in the spring, A. evonymellae cannot attack neonate P. tabaniformis larvae and must develop in alternative hosts. Prior to their death the parasitized P. tabaniformis larvae construct conical structures, 'refuges' of frass and silk threads over the external openings of the larval galleries. Apanteles evonymellae pupates in these refuges after the host's death. This modified behaviour of the parasitized host larvae probably protects the pupae of A. evonymellae from hyperparasites and predators.