Redback spiders!
Redback Spiders are found throughout Australia and are common in disturbed
and urban areas.
Identification
Redback spiders (Latrodectus hasselti) belong to the Family
Theridiidae, which is found worldwide. The notorious Black Widow Spider
(Latrodectus sp) of the United States is a close relative of the
Redback Spider, and only differs in appearance by the absence of a red dorsal
stripe. Other species of Latrodectus occur in Africa, New Zealand (the
Katipo), the Pacific Islands, Europe and North and South America.
The males' red markings are often less distinct. The body is light brown with
white markings on the upper side of the abdomen, and a pale hour-glass marking
on the underside.
Size range
1 cm (female); 3 mm - 4 mm (male)
Feeding Habits
arthropod-feeder, carnivorous, insectivorous, predator
Life cycle Once the female has mated, she can store sperm and use it over a period of up to two years to lay several batches of eggs. She spends much time producing up to ten round egg sacs (1cm diameter), which are white, weathering to brown over time. Each egg sac contains approximately 250 eggs and only one to three weeks need to pass before more eggs can be laid. These sacs are suspended within the web. Sometimes small ichneumonid wasps parasitise them, puncturing each sac with tiny holes. The young spiderlings hatch in two to four weeks. Spiderlings are cannibalistic and will eat unhatched eggs and other spiderlings. The spiderlings disperse by ballooning to another suitable nest site on long silk threads that are caught by air currents.
Females mature on average in about four months. The smaller male matures on average in about 90 days. Females may live for two to three years, whereas males only live for about six or seven months.
Mating and reproduction Male Redback Spiders do not produce a web, but may be found on the fringe of a female's web, especially during the summer mating season. The male has to make overtures to the female to discover whether she is ready to mate, which can prove fatal if she mistakes him for prey. It has been found that in order to occupy the female's attention during mating, the male spider offers her his abdomen by standing on his head and 'somersaulting' his abdomen towards her mouthparts. The female begins to squirt digestive juices onto the male's abdomen while the first palp is inserted. If he is not too weak, he will manage to withdraw, and then insert the second palp. She will continue to 'digest' his abdomen. Most males do not survive this process, which seems to be unique to Latrodectus hasselti.
Predators, Parasites and Diseases Daddy-long-legs Spiders and White-tailed Spiders are known to catch and kill Redback Spiders.
Evolutionary Relationships It was once thought that the Redback Spider, Latrodectus hasselti, was a sub species of the Black Widow Spider but it is now known to be a distinct species.
Recent research on the DNA sequences of all recognized Latrodectus species indicates that the Redback is a distinct species, most closely related to the New Zealand Katipo, and probably an Australian native.
Redbacks have most likely become much more common since European settlers started providing them with lots of the kinds of places they like to make webs in.
Danger to humans and first aid Redback bites occur frequently, particularly over the summer months. More than 250 cases receive antivenom each year, with several milder envenomations probably going unreported. Only the female bite is dangerous. They can cause serious illness and have caused deaths. However, since Redback Spiders rarely leave their webs, humans are not likely to be bitten unless a body part such as a hand is put directly into the web, and because of their small jaws many bites are ineffective. The venom acts directly on the nerves, resulting in release and subsequent depletion of neurotransmitters.
Common early symptoms are pain (which can become severe), sweating (always including local sweating at bite site), muscular weakness, nausea and vomiting. Antivenom is available. No deaths have occurred since its introduction.
Apply an ice pack to the bitten area to relieve pain. Do not apply a pressure bandage (venom movement is slow and pressure worsens pain). Collect the spider for positive identification. Seek medical attention.
Classification Species: hasselti Genus: Latrodectus Family: Theridiidae Order: Araneae Class: Arachnida Phylum: Arthropoda Kingdom: Animalia.
References
and urban areas.
Identification
Redback spiders (Latrodectus hasselti) belong to the Family
Theridiidae, which is found worldwide. The notorious Black Widow Spider
(Latrodectus sp) of the United States is a close relative of the
Redback Spider, and only differs in appearance by the absence of a red dorsal
stripe. Other species of Latrodectus occur in Africa, New Zealand (the
Katipo), the Pacific Islands, Europe and North and South America.
The males' red markings are often less distinct. The body is light brown with
white markings on the upper side of the abdomen, and a pale hour-glass marking
on the underside.
Size range
1 cm (female); 3 mm - 4 mm (male)
Feeding Habits
arthropod-feeder, carnivorous, insectivorous, predator
Life cycle Once the female has mated, she can store sperm and use it over a period of up to two years to lay several batches of eggs. She spends much time producing up to ten round egg sacs (1cm diameter), which are white, weathering to brown over time. Each egg sac contains approximately 250 eggs and only one to three weeks need to pass before more eggs can be laid. These sacs are suspended within the web. Sometimes small ichneumonid wasps parasitise them, puncturing each sac with tiny holes. The young spiderlings hatch in two to four weeks. Spiderlings are cannibalistic and will eat unhatched eggs and other spiderlings. The spiderlings disperse by ballooning to another suitable nest site on long silk threads that are caught by air currents.
Females mature on average in about four months. The smaller male matures on average in about 90 days. Females may live for two to three years, whereas males only live for about six or seven months.
Mating and reproduction Male Redback Spiders do not produce a web, but may be found on the fringe of a female's web, especially during the summer mating season. The male has to make overtures to the female to discover whether she is ready to mate, which can prove fatal if she mistakes him for prey. It has been found that in order to occupy the female's attention during mating, the male spider offers her his abdomen by standing on his head and 'somersaulting' his abdomen towards her mouthparts. The female begins to squirt digestive juices onto the male's abdomen while the first palp is inserted. If he is not too weak, he will manage to withdraw, and then insert the second palp. She will continue to 'digest' his abdomen. Most males do not survive this process, which seems to be unique to Latrodectus hasselti.
Predators, Parasites and Diseases Daddy-long-legs Spiders and White-tailed Spiders are known to catch and kill Redback Spiders.
Evolutionary Relationships It was once thought that the Redback Spider, Latrodectus hasselti, was a sub species of the Black Widow Spider but it is now known to be a distinct species.
Recent research on the DNA sequences of all recognized Latrodectus species indicates that the Redback is a distinct species, most closely related to the New Zealand Katipo, and probably an Australian native.
Redbacks have most likely become much more common since European settlers started providing them with lots of the kinds of places they like to make webs in.
Danger to humans and first aid Redback bites occur frequently, particularly over the summer months. More than 250 cases receive antivenom each year, with several milder envenomations probably going unreported. Only the female bite is dangerous. They can cause serious illness and have caused deaths. However, since Redback Spiders rarely leave their webs, humans are not likely to be bitten unless a body part such as a hand is put directly into the web, and because of their small jaws many bites are ineffective. The venom acts directly on the nerves, resulting in release and subsequent depletion of neurotransmitters.
Common early symptoms are pain (which can become severe), sweating (always including local sweating at bite site), muscular weakness, nausea and vomiting. Antivenom is available. No deaths have occurred since its introduction.
Apply an ice pack to the bitten area to relieve pain. Do not apply a pressure bandage (venom movement is slow and pressure worsens pain). Collect the spider for positive identification. Seek medical attention.
Classification Species: hasselti Genus: Latrodectus Family: Theridiidae Order: Araneae Class: Arachnida Phylum: Arthropoda Kingdom: Animalia.
References