The next time you go into the University Museum, watch out. Loxosceles laeta may be waiting for you.

Loxosceles laeta -a poisonous South American spider-has been the object of an intensive search and destroy campaign by the museum staff since 1962, and no one's sure that they've gotten them all.

Herbert W. Levi, curator of Arachnology at the comparative zoology section of the museum, first discovered the medium-sized brownish spiders in the building in 1960. After checking the building, he found it infested with the spiders. Citing a mysterious drop in the museum's silverfish population in 1937, and noting that the spiders eat silverfish, he concluded that the spiders have probably been in the museum for over 20 years.

The spiders, normally found in northern Chile and Argentina, are easily mistaken for more ordinary domestic spiders. "Everyone in the building was skeptical that the spiders were poisonous. They don't look very dangerous," Levi said.

Despite their ordinary appearance, the spider's bite produces a necrotic lesion, in which the skin and flesh in the area around the wound dies, decays, and falls away. These lesions, if not treated can result in loss ofa limb-or, in rare cases, death.

Levi said that he knew of only one possible spider victim. In 1960, a man was treated for a necrotic lesion but his case was not linked to the spiders for some time because the spiders had not yet been discovered and the lesions only develop some 15 to 20 days after the bite.

Levi's discovery in 1960 catapulted the spiders into the public eye. After a story appeared in Time magazine, the Museum staff decided to exterminate the spiders in 1962.

Three years later, Levi discovered more spiders. The building was fumigated in March of 1966, 1967, and 1968-a time of the year when spiders' food supply is low and they are easier to exterminate.

Although subsequent searches have not produced any spiders, Levi is still uncertain. "We haven't found any since, [but] it's hard for me to believe the last one's gone."