If malaria-carrying mosquitoes were wiped out, would anyone mourn the loss? Maybe one species of jumping spider would. But probably not for long.
Called vampire spiders, Evarcha culicivora lives near Lake Victoria in the East African nations of Kenya and Uganda. These spiders share the mosquitoes’ taste for human and animal blood. “This vampire spider is perhaps the only species we know that is heavily dependent on these [mosquitoes],” says Fredros Okumu. He’s a mosquito biologist. He also directs science programs at Ifakara Health Institute in Tanzania, also in East Africa. Okumu is referring to mosquitoes in the genus Anopheles. They are a main malaria spreader in Africa.
Both adult and baby spiders feast on blood. And a recent blood meal makes adults more attractive to potential mates.
But the spiders can’t get blood directly from animals or people. Their mouthparts are unable to pierce skin or hides, explains Fiona Cross. She studies spiders at the University of Canterbury in Christchurch, New Zealand. So these spiders must wait for mosquitoes to suck blood from a person or animal. Then the arachnids pounce on the flying blood bags. “We call them mosquito terminators,” Cross says.
Any blood-laden mosquito will do. But Evarcha does play favorites. Most types of mosquitoes rest with their abdomens parallel to a surface. Anopheles mosquitoes, though, sit with their bottoms sticking up in the air. That makes their blood-filled bellies more accessible. It’s especially helpful for baby spiders. They can creep right under the tilted abdomen.
Baby spiders “basically resemble dots with eight legs,” Cross says. They scuttle under the mosquito, “leap up, grab the mosquito from underneath. And as the mosquito flies away, the little spiderlings hang on with their little fangs and have just enough venom to bring the mosquito down,” she says. “They have the feast of a lifetime.”
Even so, killing off the mosquitoes wouldn’t doom the spiders, Cross says. “If Anopheles were wiped from the planet, I would say that the spiders could adapt.”