Nesting biology of Trypoxylon xanthandrum in Costa Rica with observations on its spider prey (Hymenoptera: Sphecidae; Araneae: Senoculidae).

Trypoxylon (Trypargilum) xanthandrum Richards, a spiderhunting sphecid wasp, was studied at the Organization for Tropical Studies field station at La Selva in Costa Rica. The wasps constructed nests in trap-nests with tubes 9.5, 8.0, 6.4, and 4.8 mm X 15.5 cm. Nests consisted of an inner linear series of 1-8 brood cells, usually followed by an empty vestibular cell and mud final-closure plug, placed 14 or more mm from the tube entrances. Brood cells were provisioned only with spiders in the genus Senoculus (family Senoculidae). Observations indicate that the spiders rest on the underside of branches during the day. Natural enemies of T. xanthandrum include Neochrys is (Pleurochrysis) postica (Brulle) (Hym.: Chrysididae) and Phalacrotophora punc-tiapex Borgmeier (Diptera: Phoridae).