Notes on the biology and ecology of the parasitoids of the poplar clearwing moth, Paranthrene tabaniformis (Rott.) (Lep., Sesiidae) in Bulgaria. II. Eriborus terebrans (Gravenhorst, 1826) (Hym., Ichneumonidae)

The biology and ecology of Eriborus terebrans (Grav.), a parasitoid of the poplar clearwing moth, Paranthrene tabaniformis (Rott.), were studied durin g, the period 1987-98. One-year-old poplar (Populus spp.) shoots infested w ith P. tahaniformis larvae were collected from poplar seedlings at I I loca lities in Bulgaria and examined in both field and laboratory conditions. Er iborus terebrans was recorded in seven localities as a solitary internal la rval parasitoid of P. tabanformis which developed two generations in early and mid-stage host larvae. Eriborus terebrans overwintered as a larva in P. tabaniformis overwintering larvae. In the field adult parasitoids of the o verwintering generation appeared between late April/early May, and June or July. The peak activity of E. terebrans adults only coincided with the begi nning of host emergence, which resulted in low levels of parasitism, being no more than 6.2%. Parasitoid adults of the summer generation appeared in l ate June-mid August. In this period enough larvae of the host were suitable for attacking and parasitism reached 24.4-39% in some cases, The average m ortality of P. tabaniformis overwintering larvae caused by this parasitoid in Bulgaria during the period of the study was 4.7%. A significant part of the parasitized P. tabaniformis larvae constructed tunnel structures of fra ss and silk threads over the external openings of the galleries. It is poss ible that these structures protect the parasitoid cocoons from natural enem ies hyperparasitoids and predators.