Black Widow Spider
Latrodectus hesperus
Adult female black widow spider (Clemson University, Bugwood.org)
Immature female black widow (Joseph Berger, Bugwood.org)
Adult male black widow (Whitney Cranshaw, Colorado State University, Bugwood.org)
Identification
- adult female is shiny black with a red hourglass on the underside of the abdomen (there are beneficial lookalikes without the red hourglass)
- immature females have a pale brown to black body with white to orangish banding; they get progressively more solid black as they molt toward adulthood
- males are about 1/3 the size of females and are pale brown with white markings, resembling immature females
Nesting Habits
- prefer pre-existing holes in dark, undisturbed areas
- hide during the day and are in their cobwebs at night
- common around building foundations, rock piles, wood piles, outbuildings, water meter/irrigation boxes and around exterior lighting
Diet
- insects and spiders
Significance
- can be a serious health risk, especially to children and elderly people
- bite can cause pain, nausea, cramping or death (rare)
IPM Recommendations
- Minimize nesting habitat around property.
- Seal exterior cracks and crevices to reduce hiding places.
- Regularly vacuum individuals and webs.
- Reduce clutter indoors and outdoors.
- Install tight-fitting door sweeps.
- Install tight-fitting screens in windows.
- Reduce other insects that serve as food.
- Change exterior lighting to sodium vapor bulbs.