| Latrodectus geometricus | |
|---|---|
 | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Arachnida |
| Order: | Araneae |
| Infraorder: | Araneomorphae |
| Family: | Theridiidae |
| Genus: | Latrodectus |
| Species: | L. geometricus |
| Binomial name | |
| Latrodectus geometricus | |
| Synonyms[1] | |
| |
Latrodectus geometricus, commonly known as thebrown widow,[2][3]brown button spider,grey widow,brown black widow,[3]house button spider orgeometric button spider, is one of thewidow spiders in the genusLatrodectus. As such, it is a 'cousin' to the more infamousLatrodectus mactans (black widow).L. geometricus has black and white patterns on the sides of its abdomen as well as an orange-yellow colored hourglass shape marking. Their eggs are easily identified by points that project from all over the egg sacs.L. geometricus are found all over the world, but are believed to originate in Africa or South America. Their bites, though painful, are not considered to be dangerous.
L. geometricus derives its name from the geometric patterning on its abdomen. However, the spider's coloring can and does darken over time and the pattern may become obscured.
Similar widows include theL. rhodesiensis, a brown-colored relative ofL. geometricus which is native toZimbabwe. Both species are collectively known asbrown button spiders throughout southern Africa.
L. geometricus is slightly smaller[4] and generally lighter in color than theblack widow species; the color can range from tan to dark brown to black, with shades of grey also possible. Like the black widow species in theUnited States,L. geometricus has a prominent hourglass-shaped marking on the underside of the abdomen; the brown widow's hourglass, however, is usually a vivid orange or a yellowish color. Unlike the black widow,L. geometricus has a black-and-white geometric pattern on the dorsal side of its abdomen. They also have stripes on their legs.
Brown widows can be located by finding their egg sacs, which are easily identifiable. They resemble asandspur, having pointed projections all over,[4] and they are sometimes described as "tufted", "fluffy",[4] or "spiky" in appearance. Eggs hatch in approximately 20 days.[5] Female brown widows lay about 120–150 eggs per sac and can make 20 egg sacs over a lifetime.[2]
BecauseL. geometricus is dispersed all around the globe, they have many predators. Brown widows are commonly preyed upon by different types of wasps, includingmud daubers anddigger wasps.
The brown widow has a cosmopolitan distribution.[1] TheWorld Spider Catalog gives its native distribution as Africa, with introductions to the Americas, Poland, the Middle East, Pakistan, India, Thailand, Japan, China, Papua New Guinea, Australia and Hawaii.[1] It is thought by some researchers to originate inSouth Africa,[3] although this is uncertain, as specimens were discovered in bothAfrica andSouth America.[2] They are usually found around buildings in tropical areas. They can compete with populations of the black widow spider.[6] It is found in many areas ofSouth Africa, theUnited States (including Hawaii),[2][3][4]Australia,[2]Japan,[7] theDominican Republic,[8]Costa Rica,[9] andCyprus.[2]
As of 2012, researchers at the University of California, Riverside, suggested that the brown widow spider, newly established in Southern California, may in fact be displacing black widow spiders from the region, competing and/or fighting for territory.[10][11] While certainly not definitive, this evidence does suggest that the brown widow is likely to be more hostile and aggressive towards its relative, theblack widow, than the black widow is towards it. If that proves to be true, humans may be positively affected since brown widow bites are less toxic than those of black widows, thus posing less of a threat as they displace black widows over time.[11]
Like allLatrodectus species,L. geometricus has a neurotoxic venom. The venom acts on nerve endings causing the very unpleasant symptoms oflatrodectism. However, brown widow bites are usually not very dangerous; usually much less dangerous than those ofL. mactans, the black widow.[6] The effects of the toxin are usually confined to the bite area and surrounding tissue, unlike the black widow's.[4] Mere toxicity of the venom is not the only factor in dangerousness. Brown widow bites are minor compared to black widow bites because they cannot deliver the same amount of venom as the black widow.[2] TheLD50 ofL. geometricus venom has been measured in mice as 0.43 mg/kg,[12][13]
