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Friday, May 24, 2002

ANIMAL TRACKER

Wolf spider


* Japanese name: Komori-gumo
* Scientific name: Pardosa astigera
* Description: Wolf spiders are dark brown, predatory and fast-moving spiders measuring 7-10 mm long. Females may continue to grow after they are sexually mature. They do not spin webs like many spiders. They have eight eyes, in pairs: Two large eyes facing forward provide binocular vision; four smaller eyes in a row allow closeup vision; and two slightly smaller eyes, at each side of the head, are used for scanning for predators behind and to either side. Wolf spiders often have dark stripes on the head and abdomen.
* Where to find them: On sunny, sparsely vegetated ground all over Japan. The species is sometimes gregarious, occurring in groups.
* Food: Wolf spiders got their name because they were once thought to hunt their prey in packs, like wolves. In fact, they are solitary hunters. They hunt by day, chasing down their prey -- small insects such as springtails and flies. Prey are impaled on the spider's fangs, and venom and digestive juices are injected. Once the inside of the insect has turned to soup, it is sucked dry. Wolf spiders feed in a secluded place and spend their nights in a burrow, either self-dug or one abandoned by another animal. They may use the same burrow for their whole lives. If food is scarce, wolf spiders may cannibalize immature spiders.
* Special features: Courtship in wolf spiders is complex and can be dangerous. Males try to attract females by waving their palps (sensory structures attached to the head). If the female likes what she sees, she will allow the male to transfer sperm. If not, she may eat him. The female lays eggs onto a sheet of silk and covers them with another sheet. She then picks up the bundle with her fangs and, rotating it, covers it in more silk. Finally, it is attached to the spinnerets at the rear of the abdomen. The female carries the egg sac around and can often be seen with it attached (see photo). After about three weeks, the female opens the sac and 50-200 spiderlings emerge. The spiderlings climb onto the female's back, where they will live for another week. By then, they are fully independent and able to hunt for themselves. Females produce two to four egg sacs during their two-year life span.



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