Loxosceles reclusa

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Geographic Range

Eastern Texas to western Georgia and north to southern Illinois

Habitat

Brown recluse spiders are often found around human habitations, outdoors under rocks and bark as well as indoors in houses, schools, sheds, and barns.

Physical Description

The brown recluse is about 1/2 inch long. It is brown and bears a violin-shaped dorsal stripe on its cephalothorax.

Reproduction

A courtship usually preceeds the actual mating. A male relies mostly on the fine sensory hairs that cover his body and appendages to locate a female. Along with the sense of touch, a male also has the ability to distinguish various chemical substances. Through this combined chemotactic sense, the male finds his mate by a scent that she leaves on the threads of her web or on any substratum on which she may have moved. The female would be more than likely to view an advancing male as suitable prey if she was not made aware of his presence in some way. So the male must announce himself by certain maneuvers, in which the female may later engage when she has reached a certain pitch of excitement, that are part of the courtship ritual and which, if all goes well, eventually lead to the actual mating. These maneuvres consist of the male signalling his presence by tweaking the threads of the female's snare on her web and maybe by moving his palpi and abdomen in a sort of dance. The male may perform bizarre dances, wave his palpi or legs or both, display his ornaments, and strike peculiar attitudes. If the male is successful in lulling her normal instinct to view him as prey and in stimulating her to a point where sexual union is possible, she submits to his advances and mating takes place. In most cases the sexes separate peaceably. The male may even mate again with the same female or with some other female. The actual mating takes place when the male deposits a drop of sperm on a small web that he spins before mating, and then picks up the sperm and stores it in the special cavities of his pedipalps. He inserts the pedipalps into the female genital opening when he mates to store the sperm in her seminal receptacles. There is usually a courtship ritual before mating. The female lays her eggs in a silken cocoon, which she may carry about or attach to a web or plant. A cocoon may contain hundreds of eggs, which hatch in approximately two weeks. The young usually remain in the egg sac for a few weeks and molt once before leaving it. Several molts occur before adulthood.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Behavior

During the day, a recluse spider remains in some quiet place such as a closet, beneath furniture, or in any kind of receptacle, coming out at night to search for food.

Food Habits

They feed largely on insects; they inject prey with venom that is hemolytic rather than neurotoxic. They normally eat at night.

Economic Importance for Humans: Positive

They are our allies in the continuing battles with insects. They help to control many destructive and annoying insects and pests.

Economic Importance for Humans: Negative

Their bites can be mild to serious and occasionally fatal. As of 1984, at least 5 deaths had been reported from their bites in the USA. Their hemolytic venom is dangerous. The toxins in the bite kill the cells surrounding the puncture, producing a black gangrenous spot. Often, the skin proceeds to peel away from the area around the wound, exposing the underlying tissues. In extreme cases, an area 6 inches across can be severely affected and, since the wounds are slow to heal, they leave a very unpleasant scar.

Conservation Status

The brown recluse appears to be in great abundance.

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Jane Betten (author), University of Michigan-Ann Arbor, Petra Garcia (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

native range

the area in which the animal is naturally found, the region in which it is endemic.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Bucheral and Buckley. Venomous animals and their venoms. Academic Press. vo III 1971.

Headstrom, R. 1973. Spiders of the United States. A. S. Barnes and Co., Inc., Cranbury, pp. 71-72 and p. 41

Hickman, C. and Roberts, L. 1995. Animal Diversity. Wm. C. Brown Communications, Inc., Dubuque, pp. 180-183.

Preston-Mafham, R. 1984. Spiders of the World. Facts On File Publications, New York, pp. 44 and 179.

O'Toole, C. 1986. The Encyclopedia of Insects. Facts On File Publications, New York, p. 138.

Nielsen, A. 2010. "Brown recluse spider" (On-line). Accessed March 26, 2010 at http://www.brownreclusespider.biz/.