Science Fair Project Encyclopedia
Recluse spider
The recluse or violin spider family Sicariidae contains only two genera, the infamous violin (or recluse) spiders (Genus Loxosceles), which are found nearly world wide in warmer areas, and an obscure genus of Southern Hemisphere (South America and Africa) desert spiders (Sicarius) known primarily for their self-burying behavior. Both genera have potent tissue-destroying venoms. All have six eyes arranged in three groups of two (diads) and the violin spiders are usually brownish with a darker brown characteristic violin marking on the cephalothorax. Sicarius is crab spider like and lacks this marking. Individual Sicarius can live for as much as 15 years, which makes these among the longest-lived areneomorph spiders (some tarantulas can live well over 20-30 years.) Most Loxosceles can live for one and a half to two years. Members of both genera can live for very long times without food or water.
The violin spiders include about 13 species in the United States. The Brown Recluse Spider (Loxosceles reclusa) is the best known of these. It is found in a large area of the Midwest, west to Colorado and the New Mexico state line and east to Northern Georgia. Oddly, it has been seldom collected in Florida, and then only as an incidental introduction. The venom of the Brown Recluse is highly necrotic in effect, usually causing lesions (open sores) as large as a US quarter. The wounds take a long time to heal and may require skin grafts. If these open wounds get infected there can be serious consequences. Rarely, the venom is carried by the blood stream to internal organs causing systemic effects. The South American Violin Spider (Loxosceles laeta) supposedly has a more potent venom, which results in systemic involvement more often. This spider was accidentally introduced to the Los Angeles area quite a few years ago. Other members of the genus that have been tested have venoms similar to the Brown Recluse and all members of this genus are best avoided. However, the Brown Recluse and its relatives are not very aggressive and huge populations have been found in houses where the human inhabitants were blissfully unaware of their presence!
A possible problem with diagnosing violin spider bite is that the bite of these spiders is probably both underreported in some areas and over reported generally. Unfortunately several diseases can mimic the lesions of a violin spider bite, including Lyme disease, various fungal and bacterial infections and the first sore of syphilis. Therefore it is extremely important to associate the spider directly with the bite, if at all possible.
Generally, violin spiders are usually found in the center of a sort of space web of fungal-like silk, which often contains the remains of their recent meals. For the Arizona Violin Spider (Loxosceles arizonica) the most abundant food item seems to be night-active ants like carpenter ants. The Brown Recluse is known to feed on whatever is available, and this is probably true of all sicariids.
Sicariids live in some of the driest deserts known, including the ultra dry Atacama Desert of Chile (for example, Loxosceles laeta). This ability to live in dry areas, often without food or water, allows violin spiders to hitchhike on boxes, shipping crates and other materials easily. Sicarius, which has more toxic venom than Loxosceles, based on laboratory experiments with rabbits, is found in such barren desert that humans seldom come in contact with it. It is able to bury itself partially in desert sand, like many sand-dwelling organisms. The females produce egg sacs covered with a mixture of sand and silk. The genus is considered to be a living fossil in that it is both quite primitive and distributed in parts of the former Gondwanaland, the huge southern continent that separated during the Mesozoic.
External links
- Biodiversity Explorer: Family Sicariidae (Beautiful photos of Sicarius and Loxosceles!)
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details