1 In 1997, we ran two Malaise insect traps in each of four stands of wet forest in Costa Rica (two old-growth and two 20-year-old stands) and four stands of moist forest in Panama (old-growth, 20, 40 and 120-year-old stands). 2 Wet forest traps caught 2.32 times as many ichneumonoids as moist forest traps. The average catch per old-growth trap was 1.89 times greater than the average catch per second-growth trap. 3 Parasitoids of lepidopteran larvae were caught in higher proportions in the wet forest, while pupal parasitoids were relatively more active in the moist forest. 4 We hypothesize that moisture availability is of key importance in determining parasitoid activity, community composition and trophic interactions. none