Vol. 95, No. 2. March & April 1984 47 NEST DEFENSE BY THE SOCIAL WASPS, POLISTES EXCLAMANS AND P. INSTABILIS (HYMENOPTERA: VESPIDAE) AGAINST THE PARASYTOID.ELASMUSPOLISTJS (HYMENOPTERA: CHALCIDOIDEA: EULOPHIDAE) 1 Genie G. Lutz, Joan E. Strassmann, Colin R. Hughes^ ABSTRACT: Polistes exclamans and P. instabilis were observed to remove from their nests larvae ofElasmuspolistis, and to snap at adult parasitoids. These are newly reported defenses against a parasitoid that is new to North American Polistes. Social wasps are plagued by many nest parasitoids which attack and eat brood (Nelson, 1968; Rau, 1941; Jeanne, 1979; Strassmann, 1981). Polistes employ several different defenses against these parasitoids. When adult parasitoids are detected near the nest, Polistes engage in a "parasite dance" and search all over the nest and substrate for the parasitoids (West Eberhard, 1969; Strassmann, 1981). Litte (1981) found that Mischocyttarus labiatus cut their nests down to the pedicel when phorid flies were detected nearby. Jeanne (1979) discovered that Polistes canadensis formed multiple combs to protect new brood from tineid moths infesting older cells. Starr (1976) suggested that nests of Polistes are not used for more than one season because of the parasitoids that overwinter in them. This hypothesis was supported by the observation that a population of P. annularis that was nearly free of parasitoids reused 10% of its nests (Strassmann, 1979). METHODS The observations reported here were part of a larger study of the behavior of P. exclamans and P. instabilis. A wild population of P. exclamans on the roof of the biology building at Rice University was observed in the summer of 1982. P. instabilis was observed in Puerto Oscondido, Oaxaca, Mexico in August 1983. Females were marked in both cases and nests were monitored daily. RESULTS We found that Polistes exclamans and P. instabilis actively defended their brood against Elasmus polistis, a small chalcid parasite whose larvae 1 Received October 7, 1983. Accepted December 10, 1983. ^Biology Department, Rice University, Houston, Texas 77251 ENT. NEWS 95(2) 47-50 March & April 1984
Nest Defense By The Social Wasps, Polistes exclamans And Polistes instabilis (Hymenoptera, Vespidae) Against The Parasitoid, Elasmus polistis (Hymenoptera, Chalcidoidea, Eulophidae)
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