Spidey the vampire slayer

by Aditi Mishra – A web developer, long jumper, and skilled hunter – the East African jumping spider Evarcha culicivora is a lot of things. It has a taste for the finer things in life, like extra floral nectaries, but when it comes down to business, this spider relies only on blood.

No surprises then, that this creature has a lot of cool nick names.

Meet the East African jumping spider, a.k.a. the spider terminator, a.k.a. the mosquito specialist, a.k.a. the mosquito assassin a.k.a. the vampire spider.

These spiders have earned the title of “Vampire spiders” because of their quirk of feeding exclusively on mosquitoes.

Now don’t get me wrong. Most spiders love a mosquito now and then, it makes for a lovely crunchy snack in between meals. But the East African jumping spider prefers mosquitoes exclusively over any other juicy insect. In fact, they have taste only for the female mosquitoes, the ones floating around like tiny blood bags, hence earning them their name.

Vampire spiders feed on vertebrate blood indirectly by munching on Anopheles mosquitoes. Now don’t pity the Anopheles, they are not the good guys. They prey on humans and are the chief vectors of many deadly diseases terrorizing us.

Anyway back to the main character, the vampire spiders like bloody females. In fact, they like blood so much, they dart straight for the female mosquito’s abdomen; puncturing the blood engorged belly like a juice box while the rest of her body twitches in defeat.

The vampire spider is bloodthirsty, but it does not let its bloodlust cloud its judgement. They won’t eat just any mosquito; they won’t even try to hunt the males. They hunt the females that have just had their blood meal. So much so that the red blood-filled abdomen of a female mosquito must be visible for these jumping spiders to spring into action.

But what about when the mosquito has her belly turned the other way? Surely the vampire spider won’t pass up a tasty kill, just because it cannot see the bloody belly? Would it?

Well, not exactly – because a blood engorged belly is not the only thing that the spider uses to pick its prey.

Vampire spiders are fine connoisseurs with a sophisticated palate. When unable to peer into the depths of the mosquito abdomen the spider looks at the mosquito’s head and thorax to make an educated guess. Female mosquitos’ posture and antennae differ from that of the male. They are literally a dead giveaway.

The vampire spider uses the posture and antennae as a proxy to decide if the prey is even worth the hunt. It ensures that the prey being hunted is at least a female. Something that could provide a bounty of blood, at least in principle.

But munching on blood filled mosquitoes is not only for whetting one’s appetite, it also helps them smell sexy. By eating blood-filled mosquitoes, this spider acquires a special scent – a sort of a blood perfume that is attractive to potential mates. Ahh.. the bouquet!

So, blood-fed Anopheles mosquitoes are an important sacrifice at the altar of vampire spiders’ sexiness. Age-old vampire spider mating behaviours forged by evolution. Look Anopheles, how the tables have turned now!

A red mosquito belly sure coaxes this spider into hunting. But is it enough?

How does this spider, found only on the banks of Lake Victoria in Africa, pick out mosquitoes from the general clutter of the natural world? Would tiny red speckles confuse them for instance?


Vampire spiders may not be world travellers but they certainly are sophisticated. By using a fundamental property of the Anopheles mosquitoes – basically their shape – they locate and hunt their prey.

More precisely, the spider looks for the shape of the female anopheles’ mosquito when she is resting.

The vampire spider doesn’t care how long or stubby the mosquito’s body is, the vampire spider focuses only on the angles between the most prominent body parts of the mosquito. As long as the angles are right, it is go time for the vampire spidey.

Now this is not conjecture, we know this for a fact because scientists Nelson and Yinnon dangled mosquito stick figures in front of these amazing assassins and studied them for years.

They found that the vampire spiders pounce with ferocity on the stick figures and go for the kill no matter how thick or thin the lines. It did not even deter them if the lines were disconnected. But garble the angles even a tiny bit, and the vampire spiders lose their interest and walk away to invest time in other worthy pursuits.

So, by using just a couple of simple cues like the angles of a mosquito and its antennae, the vampire spider decimates one blood thirsty mosquito after another.

Till now the vampire spider had my attention, but now it has earned my respect. If there is a Jason Bourne of spiders, this is it! What an unexpected tiny little aide in mankind’s war on mosquitoes.

But there is still one thing that doesn’t add up. Vampires feast on human blood. By that logic, isn’t the female Anopheles mosquito the vampire, and shouldn’t that make our eight-eyed, little long jumper the vampire hunter?

Hmm maybe we need to rethink the name……but for now go watch the vampire slayer hunt:


References
Dolev, Yinnon, and Ximena J. Nelson. “Innate pattern recognition and categorization in a jumping spider.” PloS one 9.6 (2014): e97819.

Nelson, Ximena J., and Robert R. Jackson. “The discerning predator: decision rules underlying prey classification by a mosquito-eating jumping spider.” Journal of Experimental Biology 215.13 (2012): 2255-2261.

Jackson, Robert R., and Fiona R. Cross. “Mosquito-terminator spiders and the meaning of predatory specialization.” The Journal of Arachnology 43.2 (2015): 123-142.

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