Monday, August 2, 2010

Nursery Web Spider

This lovely specimen is a female Nursery Web Spider, Pisaurina mira. These spiders resemble Wolf Spiders and are often mistaken for that type. Like the Wolf Spider, they are most often encountered on the ground and the female will carry around a silken bag of eggs. Where Wolf Spiders carry their egg sack attached near the end of the abdomen, the Nursery Web Spider carries hers farther forward near the center of the thoracic region. Young Wolf Spiders hatch and spend their early development hanging onto the female’s body. Nursery Web Spiders have an entirely different strategy.

As the time for hatching nears, the female Nursery Web Spider will attach her egg sack to some leaves and build a protective web that surrounds the site. The eggs will hatch and the young will spend their early days living inside this protective enclosure. The mass of young spiders can be seen in the upper left of the photo.

The mass of webbing is not so thick as to obscure the view inside. It would still be difficult for most small predators to penetrate the mass of webs and get at the babies.

The female keeps her legs anchored to the web and will respond defensively if she detects anything bothering the web.

The white mass is the remnants of the egg case. Discarded skins indicate that these spiderlings have completed one molt.

The young are quite active inside their temporary nursery. These will soon be leaving the nest to begin life on their own. They’ve reached the size where they are ready to begin feeding and their only prey inside the web is each other.


  1. Fascinating, Steve. It is so interesting to keep an eye on the different spiders around the property during the summer months. As long as they don't jump! So, until they are ready to leave the nest, is it a matter of survival of the fittest? I can hear their little screams now, "I'm not tasty, I'm your brother."

  2. Karen - In situations like this, it seems that the larger always practice their hunting skills on the smaller. That may be one of the stimuli that causes the whole bunch to scatter.

  3. One of our late-summer/fall spiders, the Green Lynx Spider, Peucetia viridens, does not carry its egg sack around (that I've seen) but does build a similar "nursery web" where the spiderlings stay for a week or so, molting frequently. When I try to photograph the spiderlings, mama spider comes to the front and threatens, while the younglings go to the far side of the web. I think of it as a spider Jungle-Gym for them to practice on, as well as protection.

    The Green Lynx Spiders also change coloration depending on what plant they're on, much like crab spiders.

  4. Elizabeth - I did some reading about this spider. It appears that I'm a little too far north for it to show up here. Sounds like an interesting species to encounter.