Black widow spider
Lactrodectus mactans
Black widow spider
Photos courtesy of: Oklahoma State University
This species is NOT in New Zealand. If you find this spider please collect a specimen carefully in a container and call Biosecurity New Zealand’s Exotic Pests and Diseases hotline on 0800 80 99 66.
Description
The black widow spider Lactrodectus mactans can be recognised by the red hourglass marking on its ventral side of the abdomen. The black widow spider is about 2.5 – 3.8 cm in body length and is a lustrous black colour except for the red coloured hourglass marking. The male usually has light streaks on its abdomen and is much smaller than the female. The female eats the male after mating. She hangs belly upward and rarely leaves the web.
Impact
The black widow is not aggressive. It will, however, bite instinctively when touched or pressed. The potency of the black widow venom is well documented. All encounters with humans and animals can be attributed to the female. Death due to widow venom is rare and in untreated patients symptoms rarely persist for more than two days.
Distribution
Eastern North America, eastern Mexico, and the West Indies
Management
Mechanical removal or destruction of these pests is the most satisfactory method of control.
Spider control can be achieved by eliminating or by treating sheltered sites with spot applications of an approved insecticide.
Resources
University of Hawaii - Knowledge Master http://www.extento.hawaii.edu/kbase/urban/site/brwidow.htm 
Virginia Cooperative Extension: http://www.ext.vt.edu/departments/entomology/factsheets/blackwid.html
Page last updated: 18 June 2008