Abstract
On the basis of 1115 records of Evarcha culicivora feeding in the field, we can characterize this East African jumping spider (Salticidae) as being distinctively stenophagic. We can also, on the basis of laboratory prey-choice experiments, characterize E. culicivora as having a specialized prey-classification system and a hierarchy of innate preferences for various categories of mosquitoes and other arthropods. Prey from the field belonged to 10 arthropod orders, but 94.5% of the prey records were dipterans. Mosquitoes were the dominant prey (80.2% of the records), with the majority (82.9%) of the mosquitoes being females, and thereafter midges were the most common prey (9.2% of the records). Preference profiles that were determined from experiments showed strong convergence with natural diet in some, but not all, instances. In experiments, E. culicivora adults appeared to distinguish between six prey categories and juveniles between seven, with blood-carrying anopheline female mosquitoes being ranked highest in preference. For adults, this was followed by blood-carrying culicine female mosquitoes and then anopheline female mosquitoes not carrying blood, but these two preferences were reversed for juveniles. Moreover, for juveniles, but not for adults, anopheline male mosquitoes seem to be a distinct prey category ranked in preference after blood-carrying culicine females and, for both adults and juveniles, preference for midges is evident when the alternatives are not mosquitoes. These findings illustrate the importance of going beyond simply specifying preferred prey categories when characterizing predators as ‘specialized’ and a need to make clear conceptual distinctions between a predator's natural diet, the prey categories that are relevant to the predator, and the predator's prey-choicebehaviour.
Highlights
Making a clear distinction between preference and natural diet is important when discussing predatory specialization [1] because, natural diet is what a predator eats in the field, preference is an inherent product of a predator’s perceptual processes, decision-making capacities and motivation
Evarcha culicivora, the predator we consider here, is an exception because a long-term research programme on this jumping spider from East Africa has allowed for large datasets from the field pertaining to natural diet and large datasets from laboratory prey-choice experiments pertaining to preferences
Determining a spider’s natural diet can be a daunting task, but perhaps less so when the spider lives in a web because identifiable prey can often be found in the web, with some web-building spiders wrapping their prey in silk and leaving it in the web as a larder to feed from at a later time [24,25,26,27]
Summary
Making a clear distinction between preference and natural diet is important when discussing predatory specialization [1] because, natural diet is what a predator eats in the field, preference is an inherent product of a predator’s perceptual processes, decision-making capacities and motivation. [2,3,4]) but often, when reading the literature on spiders and other predators, it is difficult to discern whether ‘generalist’ refers to euryphagy (i.e. inclusion of a wide range of prey in the predator’s natural diet), indiscriminate feeding (i.e. the absence of pronounced prey-choice behaviour) or some combination of the two (see [1]). It is misleading when the expression ‘generalist predator’ is used for characterizing the preychoice behaviour of salticid spiders. The methods and findings from this earlier study are strongly connected to our objectives in this study
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