Nectar feeding by wandering spiders on cotton plants

Spiders are assumed to be strictly carnivorous in assessments of their nutritional and energetic requirements, their habitat preferences, and their potential as biological control agents. However, members of Salticidae (jumping spiders), Thomisidae (crab spiders), and the fast-moving Miturgidae, Anyphaenidae, and Corinnidae, all non-webbuilding wandering spiders, have been observed at floral and extrafloral nectaries of plants, presumably feeding on nectar. To test spiders in the field for nectar feeding, we used a cold anthrone test to detect the presence of ingested fructose, a plant-derived sugar, in wandering spiders occupying cotton plants (Gossypium hirsutum L.), which have floral and extrafloral nectaries. Field collections focused on three ecologically similar, highly active nocturnal spiders: Cheiracanthium inclusum (Hentz) (Miturgidae), Hibana futilis (Banks), and H. arunda (Platnick) (Anyphaenidae). During 2002 and 2003, 27 and 21%, respectively, of all field-collected adults and subadults tested positive for fructose, indicating consumption of extrafloral nectar. In both years, significantly more females were positive than males (38 versus 11% in 2002; 26 versus 12% in 2003). Immatures tested positive at a lower rate than adults (3 and 13%, respectively). Smaller numbers of spiders in the Lycosidae, Oxyopidae, and Thomisidae were also tested. Among the thomisids, 38% in 2002 and 41% in 2003 tested positive for fructose. None of the lycosids (wolf spiders) tested positive; two of nine oxyopids (lynx spiders) did test positive. Oxyopidae is new to the list of nectarivorous spiders. These results suggest that nectarivory is common for foliage wandering spiders and may contribute to fitness.