Biology of Trypoxylon (Trypargilum) superbum (Hymenoptera: Sphecidae), a Spider-hunting Wasp with Extended Guarding of the Brood by Males

Trypoxylon (Trypargilum) superbum Julvipes (Cameron), a sphecid spider-hunting wasp, was studied at the Organization for Tropical Studies' field station at La Selva, Costa Rica. The wasps nested in trap-nests with 9.5 (N = 4) and 6.4 (N = 22) mm x 15.5 cm tubes. Nests consisted of a linear series of brood cells (X = 9.5 in 9.5 mm diameter nests, and X = 8.3 in 6.4 mm diameter nests) separated by thin mud partitions. Unlike nests of other Trypargilum, there were no thick final closure plugs and no vestibular cells. Male and female cells were generally segregated with male cells placed at the inner end of nesting tubes and female cells close to the entrance. The sex ratio based upon reared specimens was male-biased, especially in 6.4 mm diameter nests (900:222). Upon completing the last brood cell, females departed, but the males continued guarding nests until all larvae had made cocoons. Nest structure, cocoon morphology, and male behavior are discussed regarding their possible role as an adaptation against ant predation. Brood cells were provisioned primarily with spiders of the family Salticidae, but also small numbers of Ctenidae, Oxyopidae, and Araneidae. Natural enemies of T. superbum include Brachymeria sp. (Hymenoptera; Chalcididae) and Phalacrotophora punctiapex Borgmeier (Diptera; Phoridae).