Identifying the Redback

Young Redbacks and adult males

Young Redback Spiders and adult males may have considerably more pattern, and look quite different from adult females.

When newly-hatched, the young Redback is dirty-white in colour. It exhibits six black spots on the top of the abdomen and a white hourglass-shaped mark underneath.

As the young mature, they darken. The hourglass mark becomes red or orange, and the upper abdomen exhibits the characteristic red or orange stripe. The head and legs may become brown rather than black. The sides of the abdomen can be either entirely white or cream, or brown with white striations coming out from a red or orange stripe. Often the only black seen is a band beside the stripe.

Male Redback Spiders are considerably smaller than the female and are rarely seen. Small Redbacks suspected of being males are usually young females.

Adult females

The best-known image of the Redback Spider is that of the adult female, which usually has a black body and legs. The distinctive markings are on the abdomen: the upper side carries the red stripe, beginning just in front of the middle; on the underside, there is a red area in the shape of an hourglass or two triangles.

However, there are many variations on the typical pattern. The body may be generally light or dark brown; there may be red markings in front of and beside the main red band, which may be light orange or faded red.

The most dramatic variation found is that the spider may be almost entirely a light yellow-brown, so that the orange stripe is almost masked by the body colour. Throughout all of these variations, the hourglass mark on the underside is always evident to some extent. That is hardly surprising, as the hourglass mark is characteristic of Redback and Black Widow spiders throughout the world.

Not as big as you think

The abdomen of the female Redback becomes engorged when she is about to lay eggs, expanding to about 10 mm in diameter. In such gravid females, the red stripe tends to be faded and less evident.

Once the eggs are laid, the abdomen returns to its normal size and the pattern becomes more distinctive.

The overall body length is generally about 15 mm and the leg span reaches about 30 mm. Spiders much larger than this are usually Garden Orb Spiders. See Spiders frequently confused with the Redback.

A complex web and site

The web of the Redback Spider is an irregular tangle of fine but strong silk. The back portion of the web forms a funnel (visible from certain angles) where strands of silk are more closely bound. It is here that the spider and egg sacs are found.

Many spiders that are similar in shape and colour to Redbacks build similar tangled webs. However, these webs are generally weaker and usually the spider rests centrally in the open web.

Not to be confused with

It is easy to be misled in the identification of Redback Spiders. The colour of their dorsal stripe varies and this results in superficial resemblance to several other species.

The female Garden Orb Spider is one of the most deceptive. It sometimes has a broad orange or red band down the middle of the back. However, an average-sized female Garden-orb weaver is much larger than the Redback and its body (excluding the legs) exceeds the diameter of a 50 cent coin. Also, the legs are thicker than the diameter of a matchstick, whereas the legs of the Redback Spider are much thinner.

The Red House Spider - a small spider in the same family as the Redback - resembles the Redback in size, shape and general colour. However, the Red House Spider's general colour is never black, like the Redback's, and the characteristic red stripe and hourglass mark are not present.