Spiders feeding on earthworms revisited: Consumption of giant earthworms in the tropics

Predation on earthworms is common in some generalist predator species, as for example several ground beetle species (Coleoptera: Carabidae) that frequently feed on earthworms. In spiders (Araneae), however, such behavior is far less well documented. A survey of reports on spiders feeding on earthworms yielded a total of 44 naturally occurring predation events. Spiders from 14 families were observed feeding on earthworms in nature, and species from two additional families consumed earthworm prey in captivity. Earthworm predation by spiders has been observed in temperate, subtropical, and tropical regions in 18 different countries. Tropical spiders from the families Theraphosidae (Mygalomorphae) and Ctenidae (Araneomorphae) accounted for 59% of the reported predation events. Reports from French Guiana document the capture of giant earthworms (0.6-1 m in length) by the giant tarantula, Theraphosa blondi (Latreille, 1804). Predation on giant earthworms by large tarantulas has also been observed in rainforest habitats in Brazil, Ecuador, Peru, and Venezuela. Wandering spiders (Ctenidae) are known to feed on earthworms in Belize, Brazil, Costa Rica, French Guiana, Guyana, and Singapore. Quite obviously, larger-sized mygalomorph and araneomorph spiders in humid tropical rainforests are predators with broad feeding niches-including earthworms and vertebrate prey in addition to arthropod prey-and this is presumed to improve the survival of these spiders. By comparison, reports of earthworm predation in temperate climate are rarer, and recent molecular studies of the diet composition of lycosid and linyphiid spider species in Swedish arable fields suggest that earthworms are not a common prey of these species.