Unusually high numbers of the dangerous spiders have invaded between the cities of Agigea and Eforie, Gheorghe Mustata, a marine biology expert, told the Web site Hotnews.ro.

The first reports came from a teacher working with students near Agigea.

"Some 200 such spiders were seen around the Agigea beach," Mustata said. "The population must be alerted and informed" so people don't come into contact with the spiders.

Romania's unusually warm winter and extremely hot summer may have contributed to the spider explosion, he told Hotnews.ro.

The venom produced by black widow spiders is considered more potent than that produced by rattlesnakes but since the spiders are small, the bite isn't usually fatal to humans. However, bites by several spiders could prove more dangerous.