Abstract
The redback spider, Latrodectus hasseltii, is a common venomous spider in Australia. This species had not been recorded in Japan until late 1995. Large numbers of redback spiders were collected in Osaka City and in Yokkaichi City, Mie Prefecture, in November 1995. Another species of widow spiders, namely, the brown widow spider L. geometricus, was also collected in various ports : Yokohama, Tokyo, Nagoya, Osaka and in Okinawa. The author has reviewed current available information on widow spiders including the life cycle, reproduction, hunting behavior, systematics and distribution of each species, etc. The invasion route of these species into Japan is also discussed. The invasion of redback spiders into Japan apparently dates back several years as frequently old, empty egg sacs have been found. There is no information on how the redback spiders survived the winter season in Japan. Fortunately, so far in Japan no biting cases have been reported.
