San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Latrodectus geometricus
Brown Widow, brown button spider, geometric button spider

THERIDIIDAE

Description

Brown widows can vary in color intensity and pattern ranging from light tan to dark brown. There may be a red broken stripe or a series of white spots along the top of the abdomen with parallel rows of black spots on either side of the stripe. The brown color can be very dark, almost black. There is an orange hour glass mark on the underside of the abdomen in both females and males. The cephalothorax (head) is usually dark brown. Legs are usually tan and black banded.

Egg sacs are unique in their structure. Whereas black widow egg sacs are round and smooth, the brown widow sacs are round with numerous short spikes. The shape is reminiscent of WWII period sea mines. A single female can produce several egg sacs in her life time.

According to arachnologist Dr. G.B. Edwards, in Gainesville, Florida, the venom of brown widows is twice as potent as that of black widows but the effects tend to more localized than a black widow as less venom is injected. The main symptom is severe local pain. The spider is not very aggressive, does not defend its web, and bites are not common.

Range and Habitat

Brown widows apparently are originally from southern Africa. Through shipping and human migration they have become established on every continent except Antarctica. In the United States these spiders can be found in the Gulf Coast states in the southeast. Single finds have been made in Arizona and New Mexico. In southern California they have been found from northern Los Angeles County south to San Diego County and inland to Riverside County. In San Diego County they have been found from the coastal areas and as far east as El Cajon, Escondido, and Valley Center.

If you find evidence of these spiders in other areas of San Diego County such as Alpine, Pine Valley, Ramona, or Julian, please contact the Entomology Department.

The messy appearing brown widow web can be found around buildings and in gardens. Plastic lawn chairs are very popular with brown widows as are plastic flower pots with curved edges. Several widows have also been found with egg sacs in bird-of-paradise plant leaves. In general they can be found anywhere there are possible sheltered spaces for retreats.

Control

The best means of control is to remove the hiding places for spiders such as piles of wood, debris, and clutter. Plug plaster cracks, holes, and spaces around windows, doors, and walls. Routinely inspect the underside of outdoor tables and chairs. Spiders can be physically removed carefully. There are chemical controls and treatments available to control populations.

Adult female Latrodectus geometricus, copyright Jim Berrian
Adult female Latrodectus geometricus, copyright Jim Berrian

Lateral, ventral, and dorsal photographs of female brown widows.

Adult female Latrodectus geometricus, copyright Jim Berrian
Characteristic egg sac of a brown widow.

Text and photos by: Jim Berrian, Departmental Associate, Entomology Department

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