Saturday, May 10, 2008

Waiting to pounce.

One of the great things about being a human is that you are a relatively large animal and therefore not in constant danger of being eaten by something larger. The vast majority of animals are very small and feature prominently on the menu of larger predators. What is large? Spiders are large. They are among the most successful of predators, and are pretty much everywhere.



A large house spider, Tegenaria sp., Richmond, BC.

Any house has plenty of spiders. There are cobweb spiders in the crawl space, house spiders under the soffits, and jumping spiders around the windows or on the kitchen ceiling. None are particularly dangerous to humans, but that is because, again, we are large. In addition, we can defend ourselves. We have the ability to convert thumb and forefinger into a powerful spring-loaded weapon. Flick.

Most insects and other small animals have no such skill. To them, spiders are the monsters under the bed, and everywhere else. How about bees? As insects go, bees are decidedly robust, and certainly not defenceless. A spider would have to be crazy to tangle with a bee.

Not so. One group of spiders, the crab spiders, regularly dines on bees. Instead of constructing an ensnaring web, a crab spider uses itself as a trap. It lurks where a bee might land, often directly atop a colourful flower. It splays its lengthy front legs outward like the pincers of an angry crab. When a bee lands, it grabs, a classic example of what is known as a sit-and wait predator.



Crab spider, Misumena vatia. From Spider Web Watch :"The Genus Misumena is Greek for "to hate," while the specific epithet vatia is Latin for "bow-legged"."

Crab spiders have a couple of other neat tricks. One is that they can slowly change their body colour to match that of the flower. They can be white, or pastel shades of pink, yellow or pale green, the same palette as those dubious marshmallow things in Lucky Charms cereal. Some go farther, perhaps too far, mimicking bird droppings. The second trick is that their venom is particularly potent to bees, which lessens the potential for a knock-down drag-out struggle that could go the wrong way.

The crab spider in the picture is on a nine-bark bush, Physocarpus opulifolius, not about to blossom for several days. Undaunted, she has cleverly folded a leaf over herself and secured it with silk. Sooner or later, a bee will be by.

4 comments:

BerryBird said...

The crab spiders are beautiful with their varying colors. I've never noticed one curled under a leaf like that, though--great shot.

Texas Travelers said...

Great post.
As you probably know, I love spiders.

See spider post:
http://tinyurl.com/5u849g

We have posted:
Alaska's Haul Road - The Dalton Highway.
A 414 mile gravel road,
to the Arctic Ocean

Come join us for the trip,
Troy and Martha

Viooltje said...

Interesting post. And that coming from an arachnophobic gardener like me. When it comes to spiders, I also see monsters, both under and above my bed. I admire all the infatuation people have towards spiders, but somehow I have never managed to overcome my fears. If gardening has not helped so far, nothing will. Now I know they also lurk on top of flowers...lol

Wonderful blog and welcome to Blotanical!
Violet

plantgirl said...

Very cool looking spider-I learned to appreciate spiders when my husband brought home a fire leg tarantula. Wasn't so thrilled at first - but it grows on you.