There are two species of jumping spiders that specialize in hunting mosquitoes, and one of them is especially drawn to female mosquitoes filled with human blood. The findings, published in the Journal of Arachnology last month, suggest that these mosquito terminators might be natural allies in our fight against malaria.
Many spiders eat these pesky, blood-sucking vectors of disease, but according to University of Canterbury’s Robert Jackson and Fiona Cross, there are only two species that can be characterized as mosquito specialists: Evarcha culicivora and Paracyrba wanlessi.
“These two spider species are highly specialized mosquito assassins,” Cross says in a statement. “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 – mosquitoes.”
Typically found on the walls of buildings occupied by people in East Africa, Evarcha culicivora is drawn to female Anopheles mosquitoes with guts filled with (human) blood. This genus of mosquitoes transmits the malaria parasite, Plasmodium, and they’re responsible for half a million deaths a year, according to the latest estimates from the World Health Organization. “E. culicivora and Anopheles are both found in Kenya and are attracted to human odor (particularly the odor of dirty socks),” Jackson explains. “This little spider is a predator that likes us and eats our enemies.”
But while they have a taste for human blood, they’re no danger to us: They lack the mouthparts to pierce our skin and ingest our blood. And thanks to their complex eyes, these spiders can tell if a mosquito has just taken a blood meal based on the tilt of their abdomens, and then they pounce. “This is unique. There’s no other animal that targets its prey based on what that prey has eaten,” Cross tells SciDev. Furthermore, by eating blood-filled mosquitoes, these spiders of both sexes seem to acquire a “perfume” that makes them more attractive to potential mates. That means they kill blood-carrying mosquitoes for food as well as for sex.
Meanwhile, the Malaysian Paracyrba wanlessi is often found in the hollow stem (called culm) of bamboo. There, they feed on the mosquito larvae squirming on the surface of the little pools of water that have formed within the bamboo. An adult male is pictured to the right.
So, can we use these mosquito hunters for pest control? They pose no threat to us, and E. culicivora already willingly enters our houses and kills malaria vectors. “Encouraging people to welcome these guests into their homes sounds like a good idea,” the authors write. “Yet it is hard to be optimistic about educating the lay public when there are even entomologists, people who work with maggots and cockroaches, who find spiders repulsive.”
Image in text: Daiqin Li