Males also retain the white markings on the upper side of the abdomen through adulthood. Male redbacks are typically light brown in color with a dorsal red stripe and a paler hourglass shape on the ventral side of the abdomen, both of which are similar to, but less distinct than, female markings. Young female redbacks have additional white markings on their abdomens that they lose as adults. Females are typically black with a red stripe, sometimes broken, on the dorsal surface of the upper abdomen (crossing parallel to the length of the body), and a red hourglass-shaped spot on the ventral side of the abdomen. Female redbacks average 10 mm in length, with body sizes as large as a pea, and are significantly larger than males (which average 3-4 mm). Their closest relative is the North American southern black widow spider ( Latrodectus mactans), which is distinguishable from redback spiders by the absence of a red dorsal stripe. Redback spiders are bilaterally symmetrical, cold-blooded spiders belonging to the family Theridiidae. Redbacks eventually wrap up each prey item, storing some for later meals.Īnimal Foods: birds mammals reptiles insects terrestrial non-insect arthropods They do this multiple times creating a number of traps and wait for prey to run or fly into a line and get stuck. They then pull the line taut and a single trap is complete. Next, they climb up that line, adding an additional silk line on top of the original to strengthen it. They set traps for prey by bringing a strand of their silk web down and sticking it to the ground surface. At night, females construct a complex web system reaching in all directions, including towards the ground. Redback spiders catch their prey in a unique way. All redbacks have a potentially venomous bite, however only females have been known to envenomate prey. Redback spiders also steal stored prey caught in the webs of other spiders. They also sometimes catch larger animals stuck in their webs such as mice, small birds, snakes, small lizards, king crickets, Cromwell chafer beetles, and trapdoor spiders. Redback spiders are insectivores that prey on small insects caught within their webs such as ants (Formicidae spp). Negative Impacts: injures humans (bites or stings, venomous ) Other doctors are not convinced of its effectiveness in general. Recently, Australian doctors have chosen to only give the antivenom when absolutely necessary because they fear possible negative side effects. Bites that show more severe symptoms may require antivenom to be administered intramuscularly, sometimes in multiple injections. Most bites from this species can be treated with household remedies (ice packs and pain relievers). Fatalities from redback bites are rare and none have occurred since 1956, when an antivenom was created. Unlike most other envenomation syndromes, the effects of bites from this species may persist for several days, weeks, or months. More serious cases include pain lasting longer than 24 hours, bumps and swollen lymph nodes followed by sweating, a rapid heart beat, possible vomiting, headache, and insomnia. Of the remaining 20%, most feel pain radiating from the bite spot for only about 24 hours. Approximately 80% of bites cause little to no effect. Males are believed to be as capable of delivering painful, venomous bites as females, although bites are rarely reported. The main toxic component of the venom, α-latrotoxin, affects humans differently depending on the amount injected. Redback spiders can control the amount of venom that they inject and "dry" bites are not unheard of. The venom is produced in the cephalothorax and is delivered via the animal's fangs. Bites typically occur during the summer season and in the late afternoon when temperatures are highest and the spiders are most active. When disturbed, larger females often bite and envenomate intruders. Redback spiders are one of the most dangerous spiders in Australia.
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