Friday, November 27, 2009
More from Life in the Undergrowth Episode 1 - Sir Attenborough stuck his micro camera in a "harvestman" nest, and showed a male guarding a nest filled with about 25 eggs. This creature, which looked like a spider, was constantly cleaning off the eggs. Occasionally a female harvestman would stop by to mate, and she would add her eggs to his collection. This egg-sitting service was provided to more than one female. At one point, a female tried to eat one of the eggs. After the male chased her off, he scurried around and seemed to be counting the eggs to make sure they were all there. He didn't stop until he seemed satisfied that his brood was safe.
Trying to find out more about this harvestman wasn't so easy. Sir Attenborough didn't mention the particular species he was observing, and it turns out there are thousands of them. But searching around the web (no pun intended, since harvestmen don't make webs), I discovered that what he showed was most likely a Zygopachylus albomarginis.
I was surprised to find out from my research that the "American" name for a harvestman is "daddy long legs". In the UK, they use the term "daddy long legs" to refer to a crane fly. The harvestman they showed in the video did not look or act like the ones I commonly see in New Jersey. Apparently Z. albomarginis lives in Panama. The Jersey harvestmen look more like the one in the photo above, but with a more rounded and darker body.
The most surprising thing I discovered is that despite their appearance, harvestmen are not spiders! They are arachnids, so they are related to spiders, but there are some differences. Spiders have a narrow waist (pedicel) between their two body sections, breathe using book lungs (more on that here), and produce silk. They eat by piercing their prey with fangs, injecting venom and digestive juices, and sucking out the digested contents. Harvestmen have an oval body (no waist), breathe by diffusing air directly from their tracheae into their "blood" (no lungs), and do not produce silk. They also do not produce venom, so they eat by ripping their prey into small pieces and transferring these to their mouth.
I'll leave you with a fun assignment for the next time you are in the woods at night (although it may be too cold to do this now in the northern latitudes). Take a flashlight and hold the butt end against your forehead, just above your eyebrows. Point the beam of the flashlight straight out, parallel to your line of vision. Then look around until you find a set of glowing green eyes looking back at you. Walk toward the eyes, keeping the flashlight on them, and you will find a spider. No kidding!
Thanks to Wikimedia Commons for the photo.
at 12:23 AM