Posted on 11/08/2005 6:04:06 AM PST by Loud Mime
Oct. 28, 2005— Like the character Count Dracula and his real-life vampire bat counterparts, a small, East African jumping spider has a taste for blood, according to a recent study.
The spider, Evarcha culicivora, lacks the ability to pierce skin and to sip blood, so instead it feeds indirectly on blood by choosing, as its preferred meal, female mosquitoes that have just engorged themselves with a victim's blood.
The blood-hungry spider is the first predator ever identified that selects its prey based upon what the prey just ate. Similar to a protein shake, blood can be a highly nutritious drink that goes down smoothly.
"Perhaps blood is a ready-made nutrient-rich liquid meal for which minimal energy expenditure in terms of processing is needed," said Ximena Nelson, lead author of the study, published in a recent Proceedings of the National Academy of Sciences.
Nelson, a scientist at Macquarie University in Australia, and her team conducted a food preference test with Evarcha culicivora serving as the critic. They first put the spider in a glass vial so that it could not smell prey choices, which were a mixture of male mosquitoes that do not consume blood, female mosquitoes fed a sugar concoction and female mosquitoes that had just feasted on blood.
Using sight alone, the spider always chose the blood-engorged females, who looked fat and somewhat red.
The researchers next pumped odors of the mosquitoes into a test chamber that the spider entered. The spider, using only its weak sense of smell, went for the females that had just dined on blood.
Nelson told Discovery News that feeding on blood is a dangerous activity, so this spider appears to minimize its risk.
"Animals that are bitten have a reflective 'swatting' response — humans use their arms, tailed animals use their tails, etc.— and often the insect is killed," Nelson explained. "It may be safer for Evarcha to obtain blood by killing a mosquito, then risk being swatted, even if they did have the mouth parts required to pierce skin and locate a blood vessel."
The spider also uses a rather clever technique for catching its fat female mosquitoes. The spider stalks the mosquito like a cat, and then pounces either on top or underneath the mosquito before taking a bite.
With such a hunger for blood, evolution would seem to favor this spider gaining the ability to directly suck blood from victims, but Nelson thinks the way Evarcha holds its fangs might prevent this from happening.
"They hold them close to their face, not forward projecting as mosquitoes do," she said. "Perhaps they might stab themselves, and this would kill them as spiders rely on a high hydrostatic pressure inside their bodies to 'hold them up.'"
The spider, then, would sort of burst like a holiday parade balloon that has hit a pointy light post.
Steve Heydon, senior scientist and collection manager for the Bohart Museum of Entomology at the University of California at Davis, was surprised to hear of the discovery.
"I know of parasitic wasps that find their caterpillar prey based on the smell of the caterpillar's feces, but I'd never heard of a spider like this before," Heydon told Discovery News. "Spiders don't have much sense of smell, so that part of the study is especially surprising."
Heydon agrees with Nelson that spiders now probably lack the right body parts and structure to evolve into direct bloodsuckers, but he does not completely rule this out for the distant future.
"Maybe spiders will end up like bed bugs," he said. "They could have that bed-bug lifestyle of laying around and coming out at night when a big, huge, monstrous food item comes tantalizingly near them and simply goes to sleep."
OK, now that's just plain scary.
Did you see the photo?
I'll get it up here.
A mosquito-eating spider?
Send a few million down here to Louisiana.
How does the writer know that?
Br-r-r-r-r-r-r.
Evolution is surprising.
I'll take your word for it.
OH MY GOD! THat is one scary spider!
P.S. Look at his eyes. My kitten was up in my lap and I said look at the bug and pointed at my screen and she hissed!LMAO!
You are what, what you eat has eaten.
I took a quick glance at the picture....nightmare material....it has beady little eyes!
Article has ONE obvious error..Mosquitos don't have fangs..they have a probiscus..
This bring up an interesting question that I have wondered about before, if male mosquitoes do not eat blood, what do they eat?
Kittens are the coolest animals on this earth. Seeing one takes forty years off my life.
Spiders, Kittens....what a contrast!
When I was a boy scout in the Canal Zone (Panama) we camped in the jungle; Camp Chagres. We had an event we called the "Critter Crawl." A small circle, about two feet in diameter was drawn in the center of a larger circle of 25 feet. When the order was given, the kids would drop their "critters" in the center circle. Usually they kept their critter in a sack and kept it a secret until race time.
The critter that crossed the outer circle first was the winner.
But, what surprises were in store for all! Tarantulas, scorpins, snakes, iguanas.....
Make your skin crawl?
Great, just great! :-O
*shudder*
>I took a quick glance at the picture....nightmare material....it has beady little eyes!<
Hey, look on the bright side, it doesn't bite humans, it eats mosquitoes. It's ugly, yet utilitarian.
I predict this spider will get UN legal protection, which means the mosquitoes will get protection too.
They located my ex-wife?
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