What's bugging you? July 26, 2017
By Jim Leser
Published Wednesday, July 26, 2017 11:22 am
Continuing with my new series on "Beasties in the Garden," I am going to discuss a frequent resident of our gardens that most of you probably wish never set up housekeeping in your yard. I am talking about the black widow spider.
There are either three species of black widows in North America or three subspecies of a single species, depending upon which taxonomist you follow. Members of the widow genus, Latrodectus, include the southern, northern and western black widows. The western is our widow, Latrodectus hesperus.
Adult black widows are generally shiny black with a red to orange hourglass shape on the underside of their abdomen. Mature females can be as long as 1-1/2 inches if you count their legs. Males are usually about half that size and often will have red and white markings on the upper surface of their abdomen. Immature black widows can be difficult for most people to identify since they are not shiny black with a bright red hourglass. Their abdomen will often have a white color with a darker creamy stripe pattern, and their hourglass can be cream colored.
Black widows build irregular, tangled, trashy webs, usually associated with places near the ground where they can hide away from the web. These areas include woodpiles, rock walls and sometimes inside buildings, even occupied houses. Widows have poor eyesight and rely on web vibrations to detect captured prey. That is why they rush out of their hiding places when you disturb their web. They are not aggressive and are not attacking you. In fact, as soon as they detect you are not suitable prey, they scurry back to their lairs.
Male black widows are mobile, searching for receptive mates. Females that are receptive to the advances of males will place chemicals (pheromones) on their webs that will communicate to the males that they are willing mates and not hungry. This last bit of information is critical if the male suitor is to avoid becoming a meal. While sexual cannibalism is observed in the confines of the laboratory, it is rare outside in nature.
The good news is that widows kill a lot of insect pests in your gardens. The bad news is that they are a poisonous spider with venom that is said to be 15 times more toxic than that of a rattlesnake. Only female bites can be dangerous because of their large venom glands compared to males. A bite usually feels like a pin prick but then pain can radiate out from the wound sometimes causing nausea, sweating, and pain in the abdomen or back, muscle aches, hypertension or difficulty breathing. The somewhat good news is that shy widows avoid contact with us and sometimes their bites do not include the injection of venom.
In 2013, the American Association of Poison Control Centers reported 1,866 widow bites with only 14 showing severe symptoms and no fatalities. Fatalities from widow bites are extremely rare. Very young or very old individuals or those with health problems are the most likely to react badly to widow venom. But if you suspect you have been bitten by a black widow, by all means go to the hospital emergency room. Better safe than sorry and if you do suffer poisoning symptoms, the ER doctors can help relieve the pain.
Now I personally find black widows fascinating and allow them to reside in my yard. But I am careful where I stick my hands. If you or others in your household are concerned about these creatures, by all means eliminate them from your landscape. And remember, I never promised that all beasties in your garden would be welcomed with open arms by you.
Jim Leser retired to Cedaredge in 2007 after a career with Texas A&M University Extension in entomology. He is a member of the Cedaredge Tree Board and a Colorado Master Gardener.