What are Redback Spiders and How to Get Rid of them
Redback Spiders are very small and shiny, females are up to 1 cm in length while males are smaller - up to 3 - 4 mm in length. Females are black and sometimes dark brown, while males are lighter brown. The body consists of a fused head and middle section (thorax), forming the cephalothorax, and a rear section (abdomen).
At the front of the head region are four pairs of simple eyes. At the front and underside of the head are a pair of arm-like appendages (chelicerae) that attach to the fangs. Fangs are used for piercing prey and injecting venom which contains various compounds, including a neurotoxin to immobilise prey. Only females can deliver a venomous bite to humans. Redback Spiders can also spit enzymes on to their prey to aid in their digestion. Further outwards from the chelicerae are a pair of small antennae-like appendages (pedipalps) used for holding and helping to manoeuvre prey while feeding. On the underside of the cephalothorax are four pairs of long thin legs. As with all other spiders, Redback Spiders do not have antennae and are wingless.
The rear section (abdomen) is soft and rounded. The female abdomen is bulbous and rounded like a pea, whereas the male abdomen is more elongated. Females have a distinct orange-to-red and hourglass-shaped stripe starting from the middle and upper rear section (abdomen) along toward the tip and underside of the abdomen. Males have white markings with less distinct red markings.
At the tip of the abdomen are a pair of short appendages (spinnerets) which are used to produce silk. Silk is manufactured inside the abdomen from specialised silk glands. Silk is a sticky, strong and flexible substance that is used for various functions including building cocoons, nests, webs for catching and wrapping their prey. Redback Spider webs can be up to 50 cm in diameter in a haphazard, funnel-shaped and tangled design which is often connected to the ground. Webs are used as a trap to capture unsuspecting prey that walk or fly into it. Once the trap has been set off through vibrations, the Redback Spider quickly descends and wraps the prey in silken threads for later consumption.
Mating primarily occurs in summer. After mating, the female Redback Spider spins a cocoon-egg-sac in which the fertilised eggs are placed. Females can lay up to 2500 eggs in her 2 to 3 year lifetime. Eggs sacs are round, yellow-to-white, aging to brown and contain 250 eggs. Eggs are laid in webs in a warm and sheltered position. After 2 to 4 weeks, eggs hatch and juvenile spiders (spiderlings) emerge.
Spiderlings are similar in appearance to adults, only smaller and sexually immature. Spiderlings disperse and ‘fly’ away using single strands of silk elevated and transported by the wind. Spiderlings grow through many stages, shedding skin (moults) at each stage. At full maturity, adults are ready to mate and reproduce.
Redback Spiders are most active throughout the warmer months, in the early evening and during the night. Widespread throughout Australia, they are very common in urban environments.
They prefer areas that are dry and sheltered such as pot plants, letter-boxes, garden furniture, shoes, vegetable patches, piles of timber and other debris. Generally found outdoors, but may venture into the shed, garage, outdoor toilet, under the house, dog kennel or other undisturbed areas.
Redback Spiders mostly feed on insects, particularly ground-dwelling insects, other spiders and sometimes small lizards, snakes and mice. They are also known to steal prey from other webs. They can survive up to 100 days without feeding.
- Rarely ventures further than web.
- Only aggressive if disturbed.
- Solitary, but may be found in large groups consisting of the female mother and her spiderlings.
Daddy Long Leg Spiders and White-Tailed Spiders.