Monday, 11 April 2011

When is a spider not?

Best read of the day was this, thanks again BB, from the Australian Museum website. I wasn't  even aware of the Tasmanian Cave Spider... and of the fact that it is a very ancient relative of today's arachnids. It was, in effect, a spider before there were spiders. This account of the mating preparations is an eye-opener, or should that be a jaw-opener:

"Courtship and mating in the Tasmanian Cave Spider takes place from late winter to spring. The male plucks at the web and on contacting the female beats his long front legs against her, alternating with pauses or retreats - this ritualised communicating and pacifying activity may be repeated for over 5 hours. The aim is to grip the female's head in the specialised kink on the metatarsal segment of the second legs and pin her fangs apart so that mating can occur safely. The egg sacs are large (about 40 mm by 25 mm) and pear-shaped. Their structure is unusual. Within the thick, white outer silk walls, the eggs lie enclosed in a rigid, thimble-like structure, which is suspended so that it doesn't touch the outer wall. This 'thermos-like' structure may buffer the eggs against climatic changes and contaminants - the silk also seems very resistant to attack by fungi and bacteria. The female guards her egg sacs, and females living outside caves usually disguise their sacs with fragments of wet, rotting wood. Spiderlings emerge from the sacs after eight to ten months, an unusually long time, and disperse within a month. The life-span of these spiders is also long, and may prove to last several decades."
For what it's worth, these guys, even at 18cm across, are said not to be dangerous to humans, much, unless you annoy them, or are unlucky enough to shrink to their bite-size like we've seen in those movies.

1 comment:

  1. I'm glad you were entertained by the surprising Tasmanian cave spider. Where we saw then in the Blue Tier mines, there were plenty of egg sacks about, but none was included in my photos (it's difficult to aim for a flash photo in pitch darkness). Their mating arrangements are not unusual for arachnids, where mating is often fatal for the male.