Hybridization of Strains of the Gypsy Moth Parasitoid, Apanteles melanoscelus,1 and its Influence upon Diapause

Colonies of Apanteles melanoscelus (Ratzeburg) from France, Yugoslavia, and Connecticut were crossed and photoresponse curves were obtained for the 3 strains and their hybrids under laboratory and outdoor insectary conditions. Photoperiodic responses of the Connecticut strain were different from the French and Yugoslavian parasites and their hybrid. The triple hybrid was different from the French, Yugoslavian, or Connecticut strains in its diapause characteristics. The laboratory-determined critical photophases at 24°C were: Connecticut, 16-17 h; the French-Yugoslavian-Connecticut hybrid, 15 h ; French, Yugoslavian and the French-Yugoslavian hybrid, 12.5-13.5 h. Under outdoor insectary conditions, the average percentage entering diapause for each strain was: Connecticut, 96%; a newly-collected French colony, 99%; a laboratory French colony, 8% ; Yugoslavian, 8% ; French-Yugoslavian hybrid, 7%; and French-Yugoslavian-Connecticut hybrid, 30%.