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 they can be found in Florida and the Gulf states and on the west coast in southern California from Los Angeles to San Diego. It is not known how long brown widows have been in San Diego County. The first verified reproducing population was in the downtown area. They can now be found on the coast from Carlsbad to San Ysidro and as far inland as El Cajon. The natural history museum is interested in documenting the spread of brown widows in San Diego County. If you find a specimen, contact the department with details on where it was found.

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.

Lateral, ventral, and dorsal photographs of female brown widows.
Characteristic egg sac of a brown widow.