The Brown Recluse Spider (Loxosceles reclusa) belongs to the genus Loxosceles. They are also known as fiddle-back or violin spiders. Recluse spiders are a venomous genus of spider known for their venomous necrotic (death of cells and living tissue) bite. There are over 100 species of the Recluse spider, the Brown Recluse spider being the best known of the species. (Pictured left).
The Brown Recluse Spider is a reclusive creature that seeks and prefers seclusion. The Brown Recluse Spider and ten additional species of Loxosceles are native to the United States. In addition, a few non-native species have become established in limited areas of the country.
The Brown Recluse Spider is found mainly in the central Midwestern states southward to the Gulf of Mexico. Their native range lies roughly south of a line from southeastern Nebraska through southern Iowa, Illinois and Indiana to southwestern Ohio. In the southern states, the Brown Recluse Spider is native from central Texas to western Georgia. Brown Recluse Spiders are generally not found west of the Rocky Mountains. A related species, the brown violin spider, is found in Hawaii.
Brown Recluse Spider Characteristics
In the mature brown recluse spider as well as some other species of recluse spiders, the dark violin marking is well defined, with the neck of the violin pointing toward the bulbous abdomen.
The Brown Recluse Spiders colours can range from a light tan to a dark brown, however, they can also appear a deep yellow colour. Brown Recluse Spiders are covered with many fine hairs that give the spider a velvet appearance. They have long, thin brown legs which are also covered with fine hairs.
Adult Brown Recluse Spiders have a leg span of about 24 millimetres. Their body is around 3 – 8 millimetres long and about 3 – 16 millimetres wide. Males are slightly smaller in body length than females, however, males have proportionally longer legs.
Both male and female brown recluse spiders are venomous. The juvenile stages closely resemble the adults except for their size and they are a slightly lighter colour. Whereas most spiders have eight eyes, recluse spiders have only six eyes that are arranged in pairs in a semicircle on the forepart of the cephalothorax (the first (anterior) major body section), with one median pair and two lateral pairs.
Only a few other spiders have 3 pairs of eyes arranged this way, such as the Spitting Spiders (scytodids). Brown Recluse Spiders can be distinguished from scytodids as recluse spiders abdomens have no colouration pattern nor do their legs, which also lack spines.
Brown Recluse Spider Habitat and Spider Webs
The Brown Recluse Spiders habitat is usually a dark, undisturbed site which sometimes can be either indoors or outdoors. In their favoured habitats, their populations are usually dense. Brown Recluse Spiders thrive in human-altered environments. Indoors, they may be found in attics, basements, crawl spaces, cellars, cupboards and closets. Brown Recluse Spiders may seek shelter in storage boxes, shoes, clothing, folded linens, hanging picture frames and behind furniture. They also may be found in outbuildings such as barns, sheds, greenhouses and garages. Outdoors, brown recluse spiders may be found underneath logs, loose stones in rock piles and stacks of wood. Brown Recluse Spiders seem to favour cardboard when dwelling in human residences, possibly because it mimics the rotting tree bark which they naturally inhabit.
Brown Recluse Spiders build irregular webs that frequently include a shelter consisting of disorderly threads of very sticky, off-white to greyish threads. The web serves as the spiders daytime retreat and it is often constructed in an undisturbed corner in one of the locations mentioned above. Unlike most web weavers, Brown Recluse Spiders leave these webs at night to hunt. Males will move around more when hunting while females do not usually stray far from their web.
Brown Recluse Spider Diet
Like most spiders, Brown Recluse spiders mainly prey upon insects.
Brown Recluse Spider Reproduction
Brown Recluse Spiders lay eggs from May through July. The female lays about 50 eggs that are encased in an off-white silken sac that is about 2 – 3 inches in diameter. Each female may produce several egg sacs over a period of several months. Spiderlings emerge from the egg sac in about a month or less. Their development is slow and is influenced by weather conditions and food availability. It takes an average of one year to reach the adult stage from time of egg deposit. Adult Brown Recluse Spiders often live about 1 to 2 years. Brown Recluse Spiders can survive long periods of time (about 6 months) without food or water.
Brown Recluse Spider Venom
As indicated by their name, Brown Recluse Spiders are not aggressive and usually bite only when pressed against human skin, such as when tangled up within clothes, bath towels or in bedding.
Actual Brown Recluse Spiders are rare. Brown Recluse Spider bites may produce a range of symptoms known as ‘loxoscelism’ (a condition produced by the bite and characterized by a gangrenous slough at the site of bite, nausea, malaise, fever, hemolysis and thrombocytopenia).
Most Recluse Spider bites are minor with no necrosis. However, a small number of bites produce severe dermonecrotic lesions and sometimes, severe systemic symptoms. The physical reaction to a Brown Recluse Spider bite depends on the amount of venom injected and an individuals sensitivity to it.
Some people are unaffected by a bite, whereas others experience immediate or delayed effects as the venom kills the tissues (necrosis) at the site of the bite. Many Brown Recluse Spider bites cause just a little red mark that heals without event. The vast majority of Brown Recluse Spider bites heal without severe scarring.
Initially, the bite may feel like a pinprick or go unnoticed. Some may not be aware of the bite for 2 to 8 hours. Others feel a stinging sensation followed by intense pain. Infrequently, some victims experience general systemic reactions that may include restlessness, generalized itching, fever, chills, nausea, vomiting, or shock. A small white blister usually initially rises at the bite site surrounded by a swollen area. The affected area enlarges and becomes red and the tissue is hard to the touch for some time.
The bite of the Brown Recluse Spider can result in a painful, deep wound that takes a long time to heal. Fatalities are extremely rare, however, bites are most dangerous to young children, the elderly and those in poor physical condition.