SEASONAL EFFECTS ON SUPERPARASITISM BY RHAGOLETIS-COMPLETA

1. We investigate a host-parasite system in which superparasitism is a more viable strategy than is initial parasitism. Walnut husk flies (Rhagoletis completa Cresson) readily use sting holes made by conspecifics as oviposition sites. 2. Superparasitism is probably a viable strategy because husks have sufficient food for more than one fly's offspring and are difficult to parasitize initially due to the toughness of the husks. Flies preferentially attacked nuts with significantly softer husks than those which were unattacked. 3. Furthermore, flies oviposited in nuts with experimental oviposition punctures in preference to unmanipulated controls at the beginning of the season when husks were tough. However, at the end of the season when husks had softened this preference disappeared and flies readily attacked controls.