Predatory and Plant-Use Specialization by Evarcha Culicivora, an East African Salticid Spider

Abstract

Using Evarcha culicivora, a salticid spider from East Africa, my goal was to understand some of the different specific ways in which predatory specialization might be expressed. This spider was already known for its unusual prey-choice behaviour. It feeds indirectly on vertebrate blood by actively choosing blood-carrying mosquitoes as preferred prey and, as its preferred mosquitoes, actively chooses Anopheles, the genus to which all-human malaria vectors belong. Here I investigated another two distinct contexts in which predatory specialization is expressed by this species, adaptive timing of predatory activity and reliance on specific nutrients during the first active life-history stage. Using sampling procedures and experiments, I found evidence that, for E. culicivora, the timing of specifically predatory activity, not activity in general, corresponds to the time of day when its unusual preferred prey tends to be most readily available in the field. For investigating the role of different nutrients, particular attention was given to another unusual characteristic of this predator. Besides feeding on mosquitoes, E. culicivora also visits plants and feeds on nectar. In a large series of rearing experiments, I considered the effects of different feeding regimes at on E. culicivora hatchlings. Type and number of prey, as well as well as the timing of prey meals, access to plants for nectar meals, access to artificial nectar made from different sugars and amino acids and combinations of access to prey and plants were shown to influence success at completing the first instar, completion time for spiders that did succeed and longevity for spiders that failed to complete the first instar.