Wednesday, September 23, 2009

Goldenrod Crab Spider

As perhaps I mentioned before, I have been paying special attention to goldenrods this summer and fall, making many photographs for an upcoming program on the subject of these most interesting of plants.

Pay enough close attention to goldenrods and you're sure to see lots of other stuff. Insects galore are attracted to these yellow beauties, as are insect-eating arachnids.

The beautiful golden pyramidal inflorescence of Rough Goldenrod, Solidago rugosa. I came across a colony of this plant of dry sandy soils in Vinton County, and couldn't resist the opportunity to thoroughly photograph various aspects of the plants.

Although the flowers are showy and conspicuous en masse, each flower is tiny - among the smallest of any of the goldenrods. Thus, it was necessary to whip out the macro gear and move in close.

Whoa! A Goldenrod Crab Spider, Misumena vatia! These little critters are common but you'll not often see them - no explanation needed! They blend so well with the goldenrod flowers that they frequent that it is practically impossible to spot them without closely inspecting the plants. This individual is a female, and her body might be 8-10 millimeters in length. That's not very large, and you can see how tiny the goldenrod flowers are by using her as a benchmark.

Up close and personal. Oh, the joys of being an innocent nectar-loving flower fly or some other harmless six-legger. What fates await. You'd never see it coming. Ever so patient is the crab spider, not moving a muscle, just waiting for some hapless bug to bumble into range. When the victim nears, the spider will lunge and seize it with those powerful, enlarged forelegs. We're close enough in this shot to see her fangs, which will administer the coup de grace, injecting a lethal dose of venom into the once-happy bug. After sucking the contents out, the spider will leave a dessicated husk to drop to the soil, and will resume the waiting game, seeking the next meal.

Misumena vatia can also be stark white in coloration. While probably found most frequently on yellow flowers, goldenrods in particular, they also hunt on white blossoms. The ability to manipulate colored pigments allows these spiders to change color, a la chameleon, to match their substrate and more effectively ambush prey. Interestingly, the stimulus for the spider to change color is visual - signals from visual cues cause the spider to either flush the outer cells with yellowish pigment, or purge the yellow to become white. Tests have shown that spiders that were blinded did not change coloration to match their backdrop.


Janet Creamer said...

Great macro shots of the crab spider, Jim!

thegirlMJ said...

What a great blog! i'm in awe. Will definately be back for more! Thank you! ~thegirlMJ

dAwN said...

Well...I have heard of some people and things sucking the life out of you...i guess spiders do that too..
very nice post and photos...
as always a pleasure to read and learn from your blog!

Jana said...

That is some amazing adaptation. Thank you for the close-up shots.

Jim McCormac said...

Thank you. Thank you very much. I was feeling a bit crabby when I wrote about this spider; your kind remarks have bouyed my spirits. Thank you. Thank you very much :-)