They might look quite different and pounce around on different continents, but the jumping spiders known by scientists as Evarcha culicivora and Paracyrba wanlessi do agree on one thing: what's tasty. Mosquitoes.
“These two spider species are highly specialised mosquito assassins,” explains Dr Fiona Cross from New Zealand's University of Canterbury, who's been studying these gastronomically picky arachnids for some time. Together with Professor Robert Jackson, the duo recently published a review of more than 15 years’ worth of research on the spiders in the Journal of Arachnology.
While many other spider species will happily scarf down an occasional mosquito meal, these two jumpers are the only two we know about with such exclusive tastes for the insects. “Like Bram Stoker’s Dracula or Arnold Schwarzenegger in the James Cameron movie The Terminator, these little specialist predators ignore any other insects that get in the way as they pursue their target victims,” says Cross.
Each spider, however, approaches the task of feeding in its own way. Paracyrba wanlessi does its stalking in the bamboo forests of Malaysia, where it ambushes both adult mosquitoes and their larvae lurking in pools of water.
Evarcha culicivora, on the other hand, is found in the Lake Victoria region of East Africa, and it likes its dinner a little bloodier, a dietary preference that's earned it the moniker "vampire spider". Its favourite target? Female Anopheles mosquitoes that have had their fill of mammalian (that's us humans, too) blood.
This dietary quirk makes Evarcha culicivora the only animal we know of that chooses prey based on what the prey has been feeding on. The hankering for blood is so finely tuned that the spiders were able to pick out engorged female mosquitoes even when tempted by other treats in lab experiments.
And there's an additional benefit to this bloody diet: it makes the spiders smell sexier to potential mates. "By eating blood-filled mosquitoes, this spider also acquires a blood perfume that is attractive to members of the opposite sex,” explains Jackson.
But for Jackson and Cross, the investigative appeal here goes beyond just the sheer strangeness of these arachnid connoisseurs. They're also hoping the spiders have something to teach us about some of our deadliest diseases.
Mosquitoes are, after all, grimly efficient when it comes to spreading extremely harmful infections – and Anopheles mosquitoes just happen to be humankind's biggest animal foe. "[These] are the very mosquitoes notorious for being malaria vectors,” explains Jackson. That disease alone kills more than 600,000 people every year.
By looking closely at how these spiders track and hunt down their mosquito prey in the same parts of the world where dangerous tropical infections strike most often, the scientists hope to find clues that could one day help in the fight against deadly diseases like malaria.
Top header image: John Tann, Flickr