Spiders relish taste of human blood

New Zealand researchers have discovered a spider in East Africa which satisfies its craving for human blood by preying on blood-sucking mosquitos.

The spider is the only animal known to select its prey based on what the prey has eaten.

The blood-hungry spider, Evarcha culicivora, is the also first known predator that deliberately feeds on vertebrate blood by eating mosquitoes, National Geographic reports.

The finding raises the possibility that other spiders also have a taste for human and mammal blood, the researchers add.

The spider, found only around Lake Victoria in Kenya and Uganda, stalks its prey rather than trapping it in a web.

Simon Pollard, who works at the Canterbury Museum and Canterbury University, and colleague Professor Robert Jackson were last year awarded a $630,000 research grant by the New Zealand Royal Society to spend three years studying the spiders.

He said at the time that the spiders were able to pick the mosquitos replete with human blood out of a swarm, despite having only tiny brains.

"Though they are only 10mm long, they have eyesight which rivals that of primates, and can make decisions and plan ahead," he said. "These spiders have the predatory nature to rival that of a small mammal, and show evidence of complex behaviour such as making decisions."

Some of the research team's findings are published in a web page run by the United States' National Academy of Sciences.

Although no other predators are known to choose prey based on the prey's last meal, other spiders may select their victims this way, said one of the Canterbury University researchers, Ximena Nelson.

"Spiders have good chemosensory abilities, and if blood were on the menu no doubt many would be able to detect it by smell, even if not all spiders possess vision good enough to be able to detect blood-carrying prey visually," she said.

Spiders don't have the skin-piercing mouth needed to feed directly on human blood, but the mosquito-munching spider appears to have got around this by harvesting blood from the mosquitos.

The study team suspects a blood meal is also biologically important to the spider, which would normally spend a lot of energy breaking down solid food into liquid by injecting prey with digestive enzymes.

"Perhaps blood is a ready-made, nutrient-rich liquid meal," Dr Nelson said.

- NZPA