Black Widow Spiders I Have Known

Forrest M. Mims III

Black widow spiders (genus Latrodectus) are found in many countries, and five species are found in the United States, including our stretch of Geronimo Creek in South-Central Texas. Their venom is the most dangerous of any North American spider.

When we lived in New Mexico, we discovered that black widows were especially common. They construct their tangled webs under porches, in stacks of firewood and even under outhouse seats.

Black widows are ordinarily very timid. But they will aggressively protect their web, and especially their egg sack, by attempting to bite an intruder. Males are much smaller than females, which are called widows because they often consume the male after they mate.

While most black widows have a distinctive red hourglass under their abdomen, it’s important to know that some do not. I’ve seen a few of these hourglass-less specimens.

I'll never forget the day when my son Eric, then only around five years old, walked into my Albuquerque office with a plump black widow dangling from his left elbow. After I swatted the spider away and stomped it into oblivion, we noticed a red spot on Eric’s arm. The poison control center advised us to watch Eric closely for any reaction. If the spider had bitten Eric, it failed to inject any venom, and Eric experienced no effects. Had he been bitten, the effects could have been quite serious, for the black widow is among the most poisonous of spiders. Some people die of their bite.

I first became interested in the black widow when I was a student at Texas A&M University. One summer I caught a particularly nice specimen that I named Madame Fang. Her abdomen was so big that it was obvious she was close to egg-laying time, an event that I wanted very much to see. So when I went to work, I would place the jar containing Madame Fang in the refrigerator. The idea was that a chilly black widow would be less likely to lay her egg capsule.

This method worked, and Madame Fang didn't lay her egg capsule while I was at work. But I didn't get to see the actual event, because she waited until one night when I was asleep.

The refrigerator trick worked much better years later in Albuquerque. I had found a suitable black widow that was obviously close to egg-laying time, but then it was necessary to leave on a two-day business trip. So I told my wife Minnie it would be necessary to postpone the laying of the egg by temporarily placing the spider in the refrigerator.

The imminent arrival of a human baby awakens special emotions in women, so I naively assumed that would apply to arthropods as well. Of course I was wrong. Minnie was not very happy about the black widow suspended inside its mayonnaise jar in the refrigerator.

When the spider was returned to room temperature, she quickly decided to lay her egg. My camera was ready when an orange object began to emerge from her abdomen. In only seconds, a glistening amber sphere the size of a pea appeared. The spider grasped the sphere in her legs and rolled onto her back amidst the strands of her cobweb. She then attached a wide strand of silk to the egg and began rotating it with her legs just above her scarlet hourglass. Soon the egg was completely covered by a pale, tan sack of silk. The spider suspended the package in her web and stood guard.

A few weeks later, I noticed a tiny hole near the top of the egg sack. Soon a tiny, pale spiderling emerged. Another, and then another, followed. Soon the egg sack was covered by dozens of tiny, orange and brown spiders. Several of the spiderlings were twice the size of their siblings, some of whom they had apparently consumed before emerging.

Soon some of the spiders began climbing to the top of the jar, leaving behind trails of silk that others followed. When they reached the lip of the jar, they did a spider version of a handstand and let out several centimeters of silk. They then floated away on the breeze.

It was an amazing sight to see those baby spiderlings ballooning away into space. But after a dozen or so had launched into flight, I realized the neighborhood was being invaded by black widows. The invasion came to a quick halt when the jar was capped. I then retired from the hobby of observing black widow spiders, at least until the next time I had to crawl under the house to fix a water pipe.

Forrest M. Mims III and his science are featured online at www.forrestmims.org.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.