The discovery of a poisonous redback spider in the city of Kawasaki has prompted a warning from Japan's Ministry of the Environment that the invasive arachnids are gaining a firmer foothold across the nation.
Native to Australia, the first redbacks in Japan were found close to Osaka port in 1995, and it is believed they arrived aboard a freight ship from Down Under.
In the intervening years, there have been reports of the spiders being found further afield, and the specimen found in the garden of a home in Kawasaki is the closest to Tokyo to date.
The ministry issued a warning yesterday that even though the spiders are usually small - the body of the larger female of the species is usually only 1cm in length - people working in their gardens or carrying out repairs to their homes should wear protective clothing and gloves to protect themselves from bites.
With temperatures dropping as winter approaches, the spiders will be looking for warmer spots to shelter, experts say, such as in the roofs of homes or in vending machines.
The ministry added that redbacks had now been confirmed in 23 of the nation's 47 prefectures, from sub-tropical Okinawa in the south as far as Miyagi Prefecture in the north, although the majority of cases had been in western Japan, around Osaka.
The ministry's warning added that a bite from the spider - which gets its name from its distinctive markings - can cause headaches and nausea.
Bites have been known to cause paralysis or death in young children or older people.
However, deaths are rare and there have been no known fatalities since the introduction of an antivenene in the 1950s.
In September, an 86-year-old woman was bitten on the leg in the Fukuoka retirement home where she was a resident.
The woman suffered breathing irregularities, but recovered after the antivenene was administered.
A subsequent search of the property uncovered a colony of 30 spiders that were destroyed.
Many local authorities have posted information about the spiders on their websites.
The simplest way of killing the intruder, they suggest, is simply to stamp on it.