Abstract
Glyptapanteles porthetriae (Hymenoptera: Braconidae) is a solitary larval endoparasitoid of the spongy moth, Lymantria dispar (Lepidoptera: Erebidae). Previous studies suggested that only the spring generation of the wasp parasitizes early instars of L. dispar, while subsequent generations develop in larvae of unidentified alternative hosts and overwinter exclusively as endoparasitic larvae within these hosts. In a declining outbreak population of L. dispar in Austria, we observed two successive generations of G. porthetriae developing in spongy moth larvae during spring and early summer. The high abundance of parasitoids in the third outbreak year prompted us to test alternative hypotheses proposing a univoltine, monophagous life cycle with strong specialization on L. dispar. We exposed various developmental stages of L. dispar embryonic larvae to wasp females and evaluated potential dormancy induction in G. porthetriae larvae or pupae by assessing developmental parameters and respiratory activity under different environmental conditions. G. porthetriae did not develop from L. dispar individuals exposed in the egg stage, and no dormancy was observed in G. porthetriae developing in L. dispar larvae. These findings disprove the univoltine, monophagous development hypotheses and highlight the reliance of G. porthetriae on suitable alternative hosts to complete its life cycle.