Name: Brown Recluse Spider (Loxosceles reclusa)
Other names: fiddleback spider, brown fiddler, or violin spider
Scientific Classification and Taxonomy:
Lifespan: 1-2 years
Distribution: The range lies roughly south of a line from southeastern Nebraska through southern Iowa, Illinois, and Indiana to southwestern Ohio. In the southern states, it is native from central Texas to western Georgia and north to Kentucky.
Habitat: Brown recluse spiders build asymmetrical (irregular) webs that frequently include a shelter consisting of disorderly thread. They frequently build their webs in woodpiles and sheds, closets, garages, plenum spaces, cellars, and other places that are dry and generally undisturbed. When dwelling in human residences they seem to favor cardboard, possibly because it mimics the rotting tree bark which they inhabit naturally. Human-recluse contact often occurs when such isolated spaces are disturbed and the spider feels threatened. Unlike most web weavers, they leave these lairs at night to hunt. Males move around more when hunting than the females, which tend to remain nearer to their webs.
Behavior: A brown recluse's stance on a flat surface is usually with all legs radially extended. When alarmed it may lower its body, withdraw the forward two legs straight rearward into a defensive position, withdraw the rearmost pair of legs into a position for lunging forward, and stand motionless with pedipalps raised. The pedipalps in mature specimens are dark and quite prominent and are normally held horizontally forward. When threatened it usually flees, seemingly to avoid a conflict, and if detained may further avoid contact with quick horizontal rotating movements or even resort to assuming a lifeless pose (playing dead). The spider does not usually jump unless touched brusquely, and even then its avoidance movement is more of a horizontal lunge rather than a vaulting of itself entirely off the surface. When running, the brown recluse does not leave a silk line behind, which would make it more easily tracked when it is being pursued. Movement at virtually any speed is an evenly paced gait with legs extended. When missing a leg or two it appears to favor this same gait, although (presumably when a leg has been injured) it may move and stand at rest with one leg slightly withdrawn. During travel it stops naturally and periodically when renewing its internal hydraulic blood pressure that, like most spiders, it requires to renew strength in its legs.
Venom: Frequently, the bite is not initially felt and may not be immediately painful, but it can be serious. The brown recluse bears a potentially deadly hemotoxic venom. Most bites are minor with no necrosis. However, a small number of brown recluse bites do produce severe dermonecrotic lesions (i.e. necrosis); an even smaller number produce severe cutaneous (skin) or viscerocutaneous (systemic) symptoms. In one study of clinically diagnosed brown recluse bites, skin necrosis occurred 37% of the time, while systemic illness occurred 14% of the time. In these cases, the bites produced a range of symptoms common to many members of the genus Loxosceles known as loxoscelism, which may be cutaneous and viscerocutaneous. In very rare cases, bites can even cause hemolysis—the bursting of red blood cells.
Dymadex's blogs on bugs, including insects and arachnids. Insects are hexapod invertebrates like ants, beetles, bees, and flies. Arachnids are joint-legged invertebrates like spiders, scorpions, ticks, and harvestmen. Other organisms in this blog include centipede, millipede, and worms.
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