Hate spiders? The Malaysian jumping spider might just win you over. New research reveals that Paracyrba wanlessi preys almost exclusively on a despised human foe: the mosquito.
Perhaps a little respect is in order for an arachnid that gobbles up swarms of mosquitoes, the disease-transmitting insects responsible for millions of deaths a year due to malaria and other illnesses—not to mention endless annoyances on summer nights. (Related: “New Mosquito Repellent Made, ‘Better Than Anything Else.'”)
“Many other animals, including other spiders, may sometimes eat mosquitoes,” study co-author Fiona Cross, a biologist at New Zealand’s University of Canterbury and the International Centre of Insect Physiology and Ecology, said by email.
“But this spider is different, because this is a species that loves mosquitoes more than anything else!” said Cross, whose study appeared October 1 in the online journal Royal Society Open Science. (Read more about how jumping spiders travel.)
In fact, when Cross and colleagues reared spiders in the lab on non-mosquito diets and then gave the arachnids various options on the menu, they still chose mosquitoes. “This active preference for mosquitoes is highly unusual,” she said.
All Mosquitoes, All the Time
In fact, so far only one other animal is known to be such a strong mosquito specialist: another jumping spider from tropical Africa called Evarcha culicivora. This arachnid also happens to prefer Anopheles mosquitoes—the worst offenders in spreading disease, particularly malaria.
This is an example of convergent evolution; the two distantly related spiders evolved very similar traits—in this case, eating mosquitoes—independently, according to the study. (Also see “‘Surreal’ Vegetarian Spider Found—A First.”)
But at mealtime, the two spiders enlist quite opposite strategies.
“Evarcha feeds indirectly on blood by choosing blood-carrying mosquitoes as prey,” study leader Robert Jackson, also at Canterbury, said by email. “You could say the mosquito is a syringe with wings that delivers the blood to Evarcha.”
Paracyrba, on the other hand, isn’t focused on the blood content. If there’s a mosquito, empty or full, the spider targets it, said Jackson, who received funding from National Geographic Society’s Committee on Research and Exploration.
Most remarkably, the spider will eat mosquitoes of various species at all stages of life—even though juvenile and adult mosquitoes are distinctly different animals, looking almost nothing alike. A juvenile lacks wings, a proboscis, large compound eyes, and legs, and it lives in wet habitats much different from adults’ dry environs.
“Juvenile mosquitoes live in water and they are of no interest to Evarcha, but Paracyrba scoops juvenile mosquitoes out of the water,” Jackson said.
So really, Paracyrba has two kinds of preferred prey, he noted. “It chooses adult mosquitoes away from water and juvenile mosquitoes in water. This kind of double-barrel specialization on mosquitoes has never been demonstrated for a predator before.”
“Like a Miniature Cat”
The spider also has to adjust its capture style depending on the mosquito’s habitat—stalking adults on land but ambushing and repeatedly attacking juveniles from the water’s edge.
“Paracyrba [like other jumping spiders] has extraordinarily good eyesight and hunts for its prey like a miniature cat,” Cross said. (Watch a video of a jumping spider attacking a bee.)
“But even when the spider has never seen, let alone eaten, a mosquito before, and even when it has only been reared on a diet of terrestrial prey or on a diet of aquatic prey, it still knows what to do” in either scenario presented to it, she said, suggesting that the Paracyrba’s preference for mosquitoes is hardwired.
“Whether the mosquito is a juvenile or an adult, it doesn’t stand much of a chance,” she added.
Itching With Promise
Such an innate, rather extreme behavior certainly has researchers swatting around big-picture possibilities.
“Any predator that singles out mosquitoes as preferred prey has to be of exceptional interest,” said Jackson. “Mosquitoes are not just a nuisance that keep you awake at night by buzzing around your ears. These insects are also notorious vectors of malaria, dengue, and other diseases,” especially in the tropical environments where the jumping spiders live.
Of course, no one would advocate simply turning spiders loose in places where mosquitoes and the infections they spread are problematic, especially if the spiders aren’t normally there. (Also see “Hitting Mosquitoes Where It Hurts.”)
And no spider, no matter how hungry, will be a magic bullet that will rid us of mosquito-borne disease. But further study and creative thinking might suggest a role for them in solving a major public health problem. “And they are out there in nature for free,” Jackson said.
Even with big animals like lions and elephants, “it can be hard to determine how many are out and about in their natural habitat,” Jackson said.
“It’s even harder with a spider. Paracyrba is believed common in its Asian bamboo-forest habitat, but habitat destruction is happening now on such a massive scale, sometimes it’s hard to be optimistic.”
Follow Jennifer S. Holland on Twitter.