The black widow spider (Latrodectus mactans) is a sexually dimorphic spider, with the female being almost twice as big as the male and rather different in pattern and colouration (3). This species gains its common name from the common misconception that the female regularly eats the male after mating (3) (4).
The female black widow spider has a shiny black body and legs (2) (3) (4) and the underside of the body features a characteristic red hourglass-like marking (2) (3) (4), which can appear yellow or orange in certain individuals (3).
The male is also black, with a narrower abdomen than the female, and may have white lines running along the sides of its body and red spots along the centre of the upperside (2) (3) (4). It has a smaller body than the female and longer legs (3), which may have lightly coloured rings along them from earlier moults (4).
The young black widow spider is orange, yellow-white or white and gradually gains the black colouration of the adult as it ages and undergoes a series of moults (2) (3). It may also have the white stripes along the side of the body which are seen in the adult male (2).
Although there are no recognised subspecies of black widow spider, there is much variation in colour and size between southern and western populations (2).
- Female body length: c. 9 mm (2)
- Male body length: c. 4 mm (2)