Data from: Arthropod rain in a lowland tropical forest

Resource subsidies link habitats, facilitating the flow of energy across
ecological boundaries. In lowland tropical forests, "arthropod
rain" (i.e., arthropods falling from the canopy to the understory)
represents a potentially important but understudied terrestrial nutrient
flux. We investigated the composition, biomass, and environmental drivers
of arthropod rain on Barro Colorado Island, Panama. Pairs of traps–pan
traps and pole traps–placed 1 m above the ground, respectively collected
fallen arthropods and arthropods potentially climbing to the canopy.
Average (± SE) arthropod biomass density in pan traps was dominated by
Hymenoptera (primarily ants; 0.501 ± 0.023 mg dry mass m-2 day-1) and
Lepidoptera larvae (0.228 ± 0.001 mg m-2 day-1). Total dry biomass density
in pan traps was 0.896 ± 0.033 mg m-2 day-1; thus, ca. 27 kg of arthropod
biomass rains into the understory per km2 per month during the wet season
in this forest. Arthropod abundance in pan traps declined with increasing
canopy cover and increased with increasing frequency of high wind events.
By contrast, arthropod biomass density showed no relationship with canopy
cover or environmental variables. Arthropod abundance was higher in pole
traps than in pan traps and was dominated by Collembola and Acari.
Compositional overlap between pan and pole trap contents suggests that
some fallen arboreal arthropods regularly return to the canopy. These
findings illustrate an understudied pathway linking canopy and understory
food webs within tropical forests, and the complex interactions between
environmental conditions and arthropod rain.