Friday, October 26, 2007
Biodiversity Corner: Funnel web spider
Previous Halloween topics have included Dead Man's Fingers, Witches Broom, Jack-o-Lantern, and Wolf's Milk Slime all of which have nice Halloweeny names but none of them would scare anyone. Spiders on the other hand, especially large hairy ones, are a different kettle of fish. But I'm happy to say they don't scare everyone.
When and where seen. I was personally introduced to a funnel web spider on September 23 by Ailey and Ryan, two children in my neighborhood. The family had recently read Charlotte's Web so of course the kids named the spider Charlotte and they were completely unafraid of her. They would sometimes sit beside her web and eat a snack, perfectly comfortable in her presence.
You will see funnel web spiders, usually in grassy places, right up until we get a hard frost. The webs are most noticeable early in the morning when they have a coating of dew. This time last year there were dozens of them in the Towle Field. Sometimes you'll see a web on a building where there is a crevice for the funnel to lead back to, and usually where there is a light source to attract insects. Ailey and Ryan's spider had an unusual opportunity — she made her web on a garden seat and the funnel went down into a sneaker that had been left on the seat.
Distinguishing characteristics. Spiders are difficult to identify at the genus and species level. In addition to that, funnel web spiders are very quick and don't give you much time for observation. One identifier, at least at the family level, is the structure of the web. Funnel weavers are members of the Agelenidae family and they make horizontal sheet-like webs with a funnel opening usually off to one side. Another identifier is the pointy extension you can see in the photo at the end of the abdomen. This is a pair of spinnerets which are used to make silk. These long spinnerets distinguish funnel web spiders from look-alike wolf spiders which have short unobtrusive spinnerets. Wolf spiders are ambush hunters and don't build webs for capturing food. (There are a couple of exceptions in the wolf spider family but they are found in the southwest.) Like many spiders, funnel weavers are brownish and have eight eyes.
Fangs and poison. A funnel web spider is unlikely to bite a human unless it has no way to escape. They flee if threatened and lurk in their funnels waiting for prey to land on their web. When they feel the vibration on the web, they dart out, quickly determine if the item is prey, and if so bite it. The fast-acting venom immobilizes the prey in just a second or two and the spider takes it back down the funnel.
Life-cycle. Charlotte was a suitable name for Ailey and Ryan's spider since it was a female. The males are wanderers. They search for females, then mate and die. The females wait for males to find them. They fill the time spinning webs, catching food and building strength for egg laying. Sometime in fall, the females lay their eggs in disc-shaped egg sacs and die. The lifecycle is complete in one year.
Sources: Spiders and their Kin, Herbert W. Levi; American Spiders, Willis J. Gertsch; my favorite web site on invertebrates www.bugguide.net; and my friend Joe Warfel of Eighth Eye Photography who, in addition to being a masterful photographer, has extensive knowledge of spiders and their ways.
© 2007 The Carlisle Mosquito