Monday, August 3, 2015

Black Widow Meal

Black Widow hanging upside down from web with egg case - REK
Lisa Berger recently found a black widow spider in her window. Like any seasoned naturalist, she let it be and followed its progress over several days. When it captured an insect, she filmed videos of the carnage.

Wrapping up dinner - Lisa Berger
While their web detains its prey, like most other spider species widows administer the coup de grĂ¢ce by envenomation. Their chelicerae (jaws) are hollow and connect to venom glands at their base. Spiders have a very narrow intestinal tract that only accommodates liquids. It even has two filters to keep out solid particles. Digestive juices are injected into the prey, then predigested nutrients are sucked up into the intestine.

The "kiss"

The prey was bitten several times and it took a while to die. In this video you can see the final "kiss" and the spider starting to use its back leg to drag it away. It ended up in the web funnel where the widow could digest its juicy meal in relative safety.

Black widows hang upside down in their low lying web, exposing their bright red hourglass. This is thought to be an aposematic coloration, advertising their toxicity to hungry birds. Since insects see a different light spectrum than birds, it probably doesn't put off the spider's prey according to a recent study.

More on Black Widow's mating dance is in this previous blog.

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