Previous Spider Fridays:
6/02:
The Bolas Spider
5/26:
The Brown Recluse
5/19:
The Sydney Funnel-Web
5/12:
The Black Widow
I must first apologize that Spider Friday took a week off for the bustle of activity that was Yearly Kos. I felt a little like a male Wandering Spider, seeking shade in the desert heat while searching desperately for...information.
I have gotten many requests to treat various types of spiders. Among these requests the jumping spiders--family Salticidae--have had a place of prominence. The problem is, it's just too vague--there are 5026 described genera in the Salticidae. And anyway, I wanted to continue my series about spiders with unusual hunting habits.
So I said to myself: let's do both. Today, I will introduce you to the Vampire Jumping Spider--the only spider with a fondness for human blood. And when I'm done, you'll wish they were in your neighborhood--because they're quite beneficial.
TAXONOMY:
Kingdom: Animalia (Animals)
Phylum: Arthropoda (Arthropods)
Class: Arachnida (Arachnids)
Order: Araneae (Spiders)
Infraorder: Araneomorphae (True Spiders)
Family: Salticidae (Jumping spiders)
Subfamily: Plexippinae
Genus: Evarcha
Species: E. culivicora
First, a word about jumping spiders in general.
What you probably think of as a jumping spider can probably best be summarized by this picture:
(unidentified species of Habronattus genus)
They're cute. They look like they're staring at you. They're kind of funny-looking. And they jump around. Jumping spiders don't build webs--they hunt by stealth, sneaking up on prey and then pouncing on it with uncanny accuracy.
But jumping spiders are very diverse--the family salticidae has more genera in it than any other spider family. They can range anywhere from the alien-looking Lyssomanes viridis:
to the ant-mimic spiders of the genus Synemosyna:
Among other morphological features, the unifying element behind the salticidae is the arrangement of the eyes--they always will have the four big eyes in front (easily visible in the Habronattus pictured above) and four smaller eyes on the top of the carapace.
Jumping spiders have excellent vision, unlike most spiders. That helps them hunt, but it also allows for courtships rituals not seen elsewhere in the spider world! All you girls out there will wish your dates could dance as well as these guys. Check out the link for videos of male jumping spider courtship dances.
SO THEN! Let's move on to the Vampire Jumping spider, shall we?
The E. culicivora is, as stated above, in the Evarcha genus of jumping spiders. This genus is very widespread and is representative what you'd think of by an average jumping spider:
E. culicivora doesn't really have a common name--the Vampire Jumping spider is one of my own creation. It is found exclusively in Kenya and Uganda in the area around Lake Victoria.
E. culivicora has been known about for a little while, but scientists made a discovery last year that makes this little jumping spider unique--not just for spiders, but in the whole animal kingdom.
You see, the Vampire Jumping Spider has a taste for mammal blood--but specifically for human blood. Unfortunately for the spider, and fortunately for us, the spider can't get at human blood directly from us because it doesn't have the mouthparts to be able to do it.
So what does it do? It eats mosquitos, but not just any mosquito. The spider intentionally seeks out--not just by sight, but by smell as well--mosquitos of the Anopheles gambiae species, one of the prime malaria carriers of the region.
(E. culicivora with A. gambiae prey)
But it gets better! The spiders have an overwhelming tendency to eat female mosquitos already laden with blood. Male mosquitos are almost never eaten becaue they do not feed on blood.
Even more striking is that when offered a choice between a blood-fed female mosquito and a female mosquito nourished artificially with sucrose, the spider will also overwhelmingly select the blood-filled mosquito as prey. If you've ever seen a blood-gorged mosquito, you'd know that you can definitely see the abdomen swell up and turn red. Apparently, so can the spider.
And even more strange? This spider has excellent chemosensory abilities--meaning that the spider can detect the blood by smell alone, not just by sight. When scientists did a test using only the scent of a blood-filled mosquito compared with the scent of an non-blood-filled mosquito, the spider picked the room that had the scent of the blood-filled mosquito nearly every single time.
This behavior makes E. culicivora unique in the animal kingdom as the only animal on Earth that chooses its prey based on what the prey has eaten..
That really is an astonishing fact. And isn't it cute?
For an overview of the scientific study, please see, this National Geographic article.
Next week, I'll give you guys an introduction to the world's largest spider and the world's smallest spider in the size matters edition of Spider Friday.