Sunday 19 May 2013

Wolf spiders with egg sacs

Suring a sunny spell, the first wolf spider of the year carrying an egg sac - likely to be Pardosa amentata - run across the warm concrete in the garden. The silk on the egg sac was still bluish, indicating that it was very fresh. A little later I found another one sunbathing on the conservatory frame (below). A male kept approaching in full courting display mode, but she quickly lunged at him and retreated like saying 'go away, you are wasting your time'.
 Female wolf spiders as many other spiders display maternal behaviour. First, they carry their eggs wrapped in a silky egg sac until their spiderlings emerge. As these spiders move about in search of prey, this offers more protection to their eggs from casual predators than if the egg sac was attached somewhere and left on its own. Then, they open the sac when spiderligst are ready to hatch and allows them to climb on her back. The spiderlings will ride their mum for a few days before dispersing. These are sun-loving spiders, actively moving to and from sunny spots to adjust their temperature to higher than the ambient temperature in a similar way to lizards. Being carried about by their mother - both eggs and young - is likely to serve thermoregulation purposes, optimising the speed of egg and young development, as females of some Pardosa species have been shown to prefer higher temperatures than males and immatures.
Basking female.
Despite the mother's best efforts, wolf spider's egg sacs are often parasitized by tiny often flightless ant-looking wasps of the genus Gelis. Read this post by Chris Buddle to find out first hand about wolf spider egg parasites.
A Gelis wasp runs on the blue bin lid.

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1 comment:

Anonymous said...

Usually how long does it take the sac to hatch?