AUSTRALIAN REDBACK SPIDER

Family Theridiidae, Species Latrodectus hasselti

Origins

There has been debate amongst spider experts (Aranologists) as to the origins of Latrodectus hasselti in Australia. Some regard the spider as an imported variation of the North American Black Widow (Latrodectus mactans). Originally found in Queensland in the 1850s near human habitation, they were thought to have arrived by boat from Southern USA. However the distribution of this spider appears to be quite widespread throughout parts of India, the Pacific including Hawaii and New Zealand (where it is called a Katipo or night stinger.). Whatever its origins the spider is an accomplished traveller and in the 1990s an infestation was found near the airport in Osaka, Japan. Other locations in places as distant as Europe have reported redbacks. Similar species occur in South Africa.

Catching food

Most Theridid species and especially L. hasselti make very strong, very sticky snare lines. The web of redbacks is composed of a complicated mixture of proteins extruded from apparatus called spinnerets at the back end of the spider's abdomen. The web has a tensile strength the equivalent of the man- made Kevlar, coated with superglue. The spider builds a messy, tangled snare, typically underneath or inside objects and structures in and around buildings, close to the ground or other hard surfaces. The level of tangled threads has sticky trip lines attached to the ground with a weak joint at the base. When prey blunders into the trip line, sticks to the web and pulls, the line snaps and hoists the prey off the ground. The spider then descends and aids the process of entanglement and hoisting of the legless victim further into the tangle. At some point when it is safe to do so the spider will deliver a bite to kill the victim and start the process of liquefying the body of its food. Redbacks regularly snare larger victims such as ground spiders (funnel webs, trapdoors, wolf etc), large beetles and many other arthropods. There have been observations of snared small frogs, lizards and snakes.

Mating

Redbacks are commonly called "widow" spiders. The perception that the female is widowed comes from the marked size difference between the sexes. The tiny males grow to 3-4mm. Most (80-90%) of all redback males die celibate, from predation or starvation. Successful males find a home in and around the snares of females and feed on minute insects caught on the sticky web. The agile male can easily avoid the much larger female as she catches prey and adds to her snare. At maturity the male is driven to approach the female and this is done with a great degree of precision and care. After inserting his pedipalp containing his sperm packet in the female genital orifice, the male generally sacrifices himself to ensure mating success. The pedipalp is often left as a plug to block further mating. The mature female can store sperm for a long time and can produce up to 10 egg sacs, each of which can contain up to 150 eggs. The 4mm opaque sacs are hung high in the snare. The spiderlings hatch from the sac usually within 4-8 weeks but can often survive over winter in the egg sac. They disperse quickly on filaments of silk to establish elsewhere. Most spiderlings never make maturity.

Venom and bites

The venom of the redback is extremely toxic to humans, but the small amount of venom injected means the effects are rarely fatal. The molecule of the venom is large and is slow moving, causing severe local pain, swelling and often sweating. (See FIRST AID). Bites from redbacks regularly occur because people directly contact the spider. The spider's habit of hiding from sight under edges and in objects around humans means the majority of bites are on the hands. The reaction of a timid, non-aggressive spider like the redback is to avoid, move away and in a crisis, curl into a ball and fall to the ground playing dead. However, if the spider is pressed up against a surface and cannot withdraw it will deliver a bite. Redback fangs are not large and are sideways facing, making it more difficult to deliver a bite through clothing or gloves. The male is too small to bite humans. Since the development of an effective antivenene in 1956 there has been no fatalities. Prior to 1956 a total of 12 deaths had been recorded.

Predators and controls

A wide range of larger insects and spiders preys upon Spiderlings during their development. Redback spider egg sacs are parasitised by small wasps from the Braconid and Chalcid families. Some birds and lizards regard spiders, including redbacks, as food. Redbacks are human adapted and in ideal conditions can achieve high numbers around our buildings, a boon to the pest control industry. Redback numbers can be controlled by direct removal of adult and juvenile spiders and their egg sacs. Always use gloves. The spiders are generally easily located and their timid nature makes them easy to target. Whilst you may miss the occasional spider with this method it will drastically reduce numbers. It must be noted that pesticide application can prove a problem for human health. Some experts assert that pesticide usage to remove spiders is environmentally damaging, limited in effectiveness and ecologically unsound. Like all spiders, redbacks prey on many actual pests of humans.

Redback breeding at MINIBEASTS AUSTRALIA

MINIBEASTS AUSTRALIA has been supplying the tourist and educational markets with resin encapsulated redback spider specimens since 1996. In order to supply a quality product all year round and not diminish the natural habitat, Minibeasts Australia started a captive breeding program in early 1997. Since that time all our redback spider products used specimens born and raised in controlled conditions. As well as adult females we also use males and empty eggsacs in our "family" specimens. The program is currently in its 16th generation. Documentation is important and breeding records mean that every spider bred has a detailed history. Beyond a certain size, small spiderlings are separated from their siblings and housed individually. They are then fed regularly and grow to maturity within 3-6 months. Our breeding females live extended lives. Our redback spider products are sold around the world and in select retail outlets in Australia. You can order direct!

First Aid

Symptoms: Being slow-acting venom, the first symptom is a slight stinging sensation. Within an hour or so the area will swell and become tender, perhaps a white patch and variable local pain. After some hours stiffness of the area may occur, shivering and local perspiration (a symptom common only to Red Back bites). Slow degeneration over 24 hours to possible coma and death.

Treatment: Stay calm, as the effects of the bite can take hours, even days to take full effect. Usually there is adequate time to reach hospital for anti-venom treatment. The patient should be kept still, remove tight clothing, keep warm and comfortable. Ice can help alleviate pain (use a pack, never direct onto the skin).

• DO NOT elevate the wound.
• DO NOT squeeze, rub or suck the wound.
• DO NOT give fluids.
• DO NOT apply restrictive bandages due to the small amount of slow moving venom, bandaging can cause more pain.

Since the development of an effective anti-venom in 1956, no one has died from a Red Back bite.

MINIBEASTS AUSTRALIA does not intend this first aid information to be used as a definitive guide to treatment for spider bite. Refer all medical enquiries to the appropriate emergency service.