Diversidad de arañas tejedoras y su influencia sobre los insectos asociados al cultivo del cacao

Web-building spider species diversity and spatial distribution, as well their impact on insects associated to cacao foliage, was studied in a cacao orchard during the dry season. To assess impact on insect populations, the relative abundances of potential and actual prey were recorded by using the electivity index of Ivlev. A total of 1,414 spiders were sampled, representing 12 families, 52 genera and 80 species. Spider diversity and richness was higher than in coffee plantations. The nocturnal spider density on cacao crowns was about twice of those occurring during the day. Theridiidae, Uloboridae, Tetragnathidae, Pholcidae and Araneidae were the spider families with the highest abundance. Regarding insects, the orders Diptera, Hymenoptera, Coleoptera, Psocoptera and Thysanoptera represented the highest abundance in the collections. Higher numbers of spiders were found on the lower and peripheral strata of the crown. Hymenoptera, Diptera, Coleoptera, Homoptera and Thysanoptera were the most predated orders. From 36 spiders species found with prey, three species account for 50% of captured prey. The overall average predation rates were 1.68 prey per spider in one day and 17.7 X 106 prey per hectare in one year. Two insect families with known pests species (Aphididae and Scolytidae) were over-predated and most o f beneficial insect families were under-predated or only proportionally predated. Overall results showed that spiders can be considered among the natural enemies, that can function as biological control agents of cacao pests.