Redback Spider

Structure, Appearance and Characteristics

• Webbing Spider.
• Body size (approx.): Female: 12-15mm, Male: 3-4mm.
• Large females may span the size of a 50 cent coin.
• Males are much smaller and are not normally seen.
• Long thin legs (especially the first pair), tapering at ends.
• Black in colour with red or orange stripe on dorsal (top) surface. Sometimes there is a patch of the same colour on the ventral (under) side of the abdomen in an hour-glass shape. Some females are fawn coloured.
• Large bulbous abdomen.
• Small cephalothorax.
• Non-aggressive. Tend to feign death when disturbed.
• Male colouring differs from female. (White abdomen with 4 black bars on either side)
• Early instars creamy-coloured with black dorsal spots on abdomen.
• Later instars creamy with brown to black stripes and faint dorsal orange or red streak and ventral hour-glass on abdomen.
• Normally 1 generation per year. Ideal conditions can produce several egg layings in a season.
• Up to 7 spherical cocoons (up to 10mm in diameter), containing approx. 50-200 eggs are produced in the retreat during late summer.

Habitat

More abundant in warm, dry areas. Occur under or amongst stones, logs, mallee roots, loose bark, in hollow logs, occasionally amongst foliage but always with some pare of the web in contact with the ground. Frequently around habitations in boxes, tins, farm machinery, sheds, outdoor toilets, around window sills and crevices in bricks. Web consists of a retreat funnel, and several tough strands to the ‘snare’, which is an irregular tangle having vertical threads in contact with the ground. The retreat may be over 3 metres from the snare in order to find a secluded area.

Pest Status

Female bites are very painful and can cause illness or death. The bite is often felt initially as a mild sting, although some victims have reported a burning sensation around the bite area. In most cases, intense local pain is experienced about five minutes after the bite. The main indication of a Redback Spider bite is localized seating at the bite site. Other symptoms can include muscular weakness, lack of coordination, paralysis and tremors. Nausea, vomiting, local swelling, dizziness or fainting, fever and muscular spasms have also been recorded Male does not bite. Webs can be unsightly on structures. Adults are considered the pest.