Mosquito-specialist spiders

What does ‘mosquito specialist’ mean? A mosquito specialist is a predator that actively prefers mosquitoes, by which we mean that it is differentially motivated to capture mosquitoes among possible prey. This would make it extraordinarily useful, as it would be targeting an insect that matters to people. At best, the mosquito is a nuisance and, at worst, it is a notorious disease vector. There may be many predators that eat a lot of mosquitoes, but experimental evidence is needed to show that a predator has the sensory capacity to distinguish mosquitoes from other prey and that it deploys a strategy of choosing this specific prey type. There is one predator for which the required evidence is actually available: its name is Evarcha culicivora (Figure 1), a jumping spider (family Salticidae) from the Lake Victoria region of East Africa. All salticids are remarkable predators because, thanks to their unique, complex eyes, they can see with a level of spatial acuity unrivalled by other animals in their size range and they deploy intricate visionguided stalking strategies. However, E. culicivora seems to have taken seeing detail to a level that is extreme even by salticid standards. The shoreline of Lake Victoria teems with insect life, especially chironomid and chaoborid midges, which vastly outnumber mosquitoes. These midges are known locally as ‘lake flies’, and they resemble mosquitoes. E. culicivora preys on lake flies and other insects, but it prefers mosquitoes — it can identify a mosquito in a crowd by sight alone, even when the insect is entirely motionless. However, E. culicivora’s target is actually even more specific and this specificity is part of a strategy of feeding indirectly on vertebrate, including human, blood.