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HumBug: Butterfly vs. Spider

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Female crab spider with a cabbage butterfly. - ANTHONY WESTKAMPER
  • Anthony Westkamper
  • Female crab spider with a cabbage butterfly.
A snout moth. - ANTHONY WESTKAMPER
  • Anthony Westkamper
  • A snout moth.

Some time ago, I mentioned in passing that butterflies and moths are covered with scales and fine hairs. They are easily dislodged and I theorized that these easily discarded structures might serve them as a release mechanism from sticky traps like a spider's web. Last night I noticed a small cross orbweaver (Araneus diadematus) in the middle of its web. Attracted to my flashlight, a snout moth (family pyralidae) stumbled into the web, fluttered once, broke free and left. The impact zone was covered with flakes and fine hairs. Like trying to stick duct tape to talcum powder, the particles had adhered to the spider's adhesive, pulled off the insect, and allowed it to escape unscathed. 
Snout moth scales in spider's web. - ANTHONY WESTKAMPER
  • Anthony Westkamper
  • Snout moth scales in spider's web.

Considering that spiders consume somewhere between 500 and 800 million tons of insects annually, this ability to escape sticky web snares may contribute to the success of everybody's favorite order of insects, Lepidoptera.
Much smaller male crab spider with prey on a daisy. - ANTHONY WESTKAMPER
  • Anthony Westkamper
  • Much smaller male crab spider with prey on a daisy.

Female crab spiders, Misumena vatia, have a different approach to hunting. They are camouflaged ambush predators — eschewing a web, they wait patiently on flowers for insects to come to them. As a hunter that actually grapples with her prey, she is equipped with strong front legs and a powerful venom to disable it quickly, avoiding injury to herself.
A camouflaged female crab spiders stands out at night under black light. - ANTHONY WESTKAMPER
  • Anthony Westkamper
  • A camouflaged female crab spiders stands out at night under black light.
The same spider under white light. - ANTHONY WESTKAMPER
  • Anthony Westkamper
  • The same spider under white light.

The females have a limited ability to change colors from white to yellow and back again, but it takes days or even weeks to accomplish. In the perpetual arms race of evolution, this species has arrived at a counter for the butterfly's defense.
Yellow crab spider. - ANTHONY WESTKAMPER
  • Anthony Westkamper
  • Yellow crab spider.

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