Scientific Name
Latrodectus geometricus
Common Name
Brown Widow
Other Names
Brown Button Spider, Geometric Button Spider, Gray Widow
Explanation of Names
- Author: Carl Ludwig Koch. First year published: 1841, as Latrodectus geometricus.
- Pronunciation: Lat-row-DEK-tus gee-oh-MET-rik-us
- Meaning: Latrodectus is Greek for “biting in secret” (this refers to the painlessness of the initial bite and the fact that it often goes unnoticed until symptoms present). The intended meaning of geometricus is currently unknown, as C. L. Koch did not mention it in his original description. It’s possible to piece together some guesses from the Latin and Greek roots, but they would be pure speculation. Often the literal translation is not the author’s intended meaning, for one reason or another.
Appearance
- Size: Body length of mature female 7-10 mm; male 2-3 mm.
- Color: Most mature specimens have the abdomen entirely golden brown or silvery gray with dorsal spots of orange or white and lateral white stripes with black spots. The carapace is dark brown. Legs are typically brown banded with black. Specimens darken as they age, and some entirely black individuals have been recorded. An orange-red hourglass marking is present on the underside of the abdomen.
- Eyes: Eye arrangement typical of cobweb weavers (family Theridiidae), except that the lateral eyes are completely separated from each other. Total of eight eyes divided in two horizontal rows of four.
- Legs: Front pair of legs is longest, third pair shortest, typical of the family Theridiidae. Legs long in proportion to body and lack obvious spines.
- Body: Abdomen of mature females is usually globose, much larger than the cephalothorax. Abdomen of males is smaller, more oval, and tapered toward the rear.
Range
Probably native to Africa, this species is now found almost globally in subtropical regions. It ranges across the southern third of the U.S., especially in the southeast. Recently, it has been recorded commonly in southern California, with scattered records in Arizona, Nevada (Las Vegas), and elsewhere. Its affinity for manmade structures and objects has facilitated its expanding distribution via commerce.
Habitat
This spider may be common in yards and gardens, often building its web in more exposed situations than other widow spiders. Be careful handling objects that have been undisturbed outdoors for long periods, such as children’s toys and playground equipment, gardening pots, and buckets. This spider thrives in a Mediterranean climate.
Web
The Brown Widow spins an extensive, tangled, three-dimensional “cobweb” snare. The threads are extremely strong and elastic, and can be plucked like guitar strings without breaking. The lines anchored to the ground (or lowermost substrate) are the trap lines. Insects, or other spiders, that trip the lines become entangled. The rebounding silk yanks the victim into the body of the web where the spider apprehends it. Flying insects may also be intercepted by the body of the web. At rest, the spider usually retires into a funnel-like retreat in a crevice or beneath an object. The spider may also rest upside down in the body of its web at night. Webs are frequently associated with manmade structures in the United States.
Season
Mature individuals may be found in nearly all seasons.
Food
Prey is almost any insect or spider or other small animal that becomes entangled in the snare. There is at least one record of a small toad becoming entangled in a brown widow web and subsequently killed.
Life Cycle
Egg sacs are nearly spherical, brown or beige tufted objects that may be the best clues in identifying this species when the spider itself is not present. Each egg sac contains an average of about 80 eggs, but a female can produce up to 20 egg sacs in her lifetime.
Remarks
This species is a potentially dangerous spider. Its venom is neurotoxic, and while it is likely to be as virulent as that of other widow spiders, bites usually result in only localized pain and swelling. The Common House Spider, Parasteatoda tepidariorum, is frequently mistaken for the Brown Widow, but the Common House Spider lacks the red or orange hourglass marking on the underside of its abdomen.
