We investigated changes in the abundance of vespid wasps responding to mast fruiting that occurred in 1996 in a lowland tropical rainforest of Peninsular Malaysia, using Malaise traps from 1995 to 1997. The nocturnal vespine wasp (Provespa anomala) and polistine wasps were collected throughout the trapping period, without any distinct changes in abundance. True hornets (Vespa mocsaryana, V. tropica leefmansi, and V. multimaculata pendleburyi), however, were trapped only in several months during or just after the mass falling of fruits. Mast fruiting may temporally increase the population of Vespa hornets that depend on ripe fruits as carbohydrate sources.