Printable brochure on Black Widows 

Black Widow Spider      

Latrodectus hesperus

Biology Black widow

The most common dangerously poisonous spider in California is the Black Widow.  Like all spiders, it has eight legs and two major body sections.  The adult female has a rounded, glossy black body.  Usually there is an orange to red marking resembling an hourglass on the underside of the body.  Adult females, including the legs, are about the size of a quarter.  Male spiders and immature females are much smaller and have brownish white stripes along the sides of the body.  Black widows construct a loose, but strong, irregular web in protected, dark areas such as the corners of sheds, behind furniture, under woodpiles, and in thick vegetation.  The egg case is about the size of a marble, and is yellowish and fuzzy.  A person bitten by this spider should immediately seek medical attention in case of an adverse reaction to the venom.

 Control  Entry of black widows into the home can be minimized by ensuring that window screens fit tightly,  and by keeping doors closed as much as possible.  There are several insecticides available that will reduce infestations of spiders with repeated applications, as spiders are difficult to kill.  In cases of isolated spiders, simply smashing the spider and the egg case with a fly swatter works well.   

Printable brochure on Black Widows 

West Valley Mosquito and Vector Control District