Microstigmus comes Wasps have a Method of Nest Construction Unique Among Social Insects

Abstract

As many as six females of the Neotropical wasp, Microstigmus comes, cooperate to gather and silk a single ball of material derived from the underside of fronds of the host palm, Chiyosophila guagara. They mold this into a bag, then lower it on a silked petiole which is finally given a characteristic spiral. Construction averaged 36.8 hours of working time performed over four days. Orphaned wasps initiated new nests on their original host plant 75 percent of the time. Heavy rain and winds destroyed 28.6 percent of newly established units. THE NEOTROPICAL WASP, MICROSTIGMUS COMES Krombein, is the most socially advanced member of the Sphecidae (Matthews 1968a), with as many as 18 adults of both sexes sharing a nest. Members of this species nest only on the undersides of fronds of the palm Chbyosophila guagara Allen, which occurs abundantly in the lowland rain forests of the Osa Peninsula of Costa Rica. Unique, pendent, bag-like nests, each suspended by a narrow petiole, are constructed from waxy vestiture scraped from the underside of the palm frond and bound together with silk that female wasps secrete from abdominal glands (Matthews 1968b). While the details of nest initiation are well established for most social vespid wasps, the manner of M. comes nest construction has been heretofore unobserved. At Sirena, Corcovado National Park, Costa Rica, we observed various stages in the construction of 2 5 M. comes nests during October 1980, March 1981, and September 1981. These were discovered in the course of monitoring over 200 active nests as part of a long-term study of the social biology of this species. In August 1982, we observed and filmed the complete construction sequence for five nests, which wasps initiated after their original nests were destroyed. All behavioral observations were made in the natural setting, and details of some rapid behaviors were determined with motion or still photography.