Evarcha culicivora is a jumping spider native of Kenya, where it is also known as the vampire spider, because of the bloody menu it craves. These spiders have a strong preference for female blood-fed Anopheles mosquitoes, which they sort out from swarms of other similarly sized insects.
The research, led by Ximena Nelson and Robert Jackson, from the University of Canterbury, New Zealand, was published on the latest issue of the Journal of Experimental Biology (JEB).
How do they manage this? The secret, it seems, is in the antennae of their victims. "The bodies of Anopheles mosquitoes rest on a 45deg angle from the substrate but most others rest parallel", Ximena Nelson explains. "Obviously, blood-fed females have an engorged red abdomen and the other difference that comes to mind between males and females is the antennae", says Nelson. Male Anopheles have luxuriant fluffy antennae, whereas females do not, so the authors designed an ingenious experimental set-up to test just what makes these spiders jump for a bite.
The researchers created "Frankenstein mosquitoes", with "blood-engorged female abdomens and male antennae, slender male abdomens and female antennae, and every other combination in between", according to a press release from JEB. Then they presented these hybrids to the spiders, and tested their preferences.
Their results show that the spiders prefer blood-engorged females, and that they detect them by their antennae.
As explained in their press release:
"The great thing about jumping spiders is they're very decisive', recalls Nelson, who could clearly see that the spiders preferred intact blood-engorged females over everything else, even females engorged with transparent sugar solution. And, when Nelson offered the spiders the choice between a Frankenstein female (made from the head and thorax of one female fused to the blood-engorged abdomen of a second female) and a hybrid constructed from a male head-and-thorax and a blood-engorged female abdomen, the spiders usually selected the hybrid with the female antennae, even though both hybrids were packed with blood. Also, when she tempted the spiders with animated simulations of blood-engorged mosquitoes with either male or female antennae, the spiders consistently pounced on the simulated female."
For more information, and the original article go to: http://jeb.biologists.org/content/215/13/i.1