Plant nectar increases survival, molting, and foraging in two foliage wandering spiders

We predicted that because plant nectar is high in energy, it is likely to provide multiple benefits to spiders that spend a substantial amount of energy foraging. In three laboratory experiments, we tested the effects of dietary extrafloral nectar on the survival, molting, and activity of two foliage wanderers, Cheiracanthium mildei L. Koch 1864 (Miturgidae) and Hibana velox (Becker 1879) (Anyphaenidae), both highly active, quick-moving nocturnal foragers. Extrafloral nectar contributed significantly to survival and molting in prey-deprived H. velox. On a marginal diet of prey (one Drosophila adult on alternate days) offered to spiders as soon as they emerged, 97% of C mildei underwent their first molt if they also received nectar, compared to 7% of controls without nectar. On a marginal diet of prey (one Drosophila adult on alternate days) offered to spiders starting two days after their emergence, 78% of the spiders also receiving nectar molted, compared to 0% of controls without nectar. Video recordings of activity showed that prey-deprived groups of C mildei maintained their active nocturnal foraging for many days on nectar, whereas controls became increasingly quiescent until they died. Non-web-building spiders that feed on nectar may utilize its energy for foraging and thereby allocate the nutrients of prey to maintenance and growth.