When red legged spider wasps occur indoors, they often end up stinging someone. Although not as painful as a red wasp sting, the sting is moderately painful, and it usually comes as surprise. These pint-sized wasps (about ½ to 3/4 inches long) are occasionally seen inside homes and other buildings, flying from spot to spot, crawling about a bit, then flying to the next spot. Unlike most other wasps, which tend to start looking for a way out when they find themselves trapped inside a building, red legged spider wasps behave as if they are still hunting for spiders. Because these are solitary wasps, they are not aggressive, and they do not “go looking for people to sting.” But they will land and crawl on people as they fly about searching for spiders, and stings occur when wasps get trapped between clothing and skin, or when someone absent-mindedly brushes their hand over one that is crawling on their head or the back of their neck.
Although they hunt a variety of spiders, red legged spider wasps are especially fond of jumping spiders. After paralyzing the spider with their sting, they usually use their mandibles to remove the legs and then carry the paralyzed spider back to their nest. The nests are small, barrel-shaped mud tubes, but these are usually constructed inside some larger hole or crevice. One of their favorite nest sites is an abandoned mud dauber nest, which they adapt for their own use, provisioning galleries with amputated spiders and laying an egg in each gallery. The resulting spider wasp larvae feed on these spiders just as mud dauber larvae feed on the spiders their moms leave for them. Even though both wasps feed on spiders, they tend to hunt different types of spiders, which limits competition for food. Red legged spider wasps will also nest in small, appropriately-sized holes and crevices. There are other species of small spider wasps in this genus that behave similarly but do not have the red legs.
Control: Its uncommon to see more than one or two of these little wasps a year, but when they occur inside, it is best to go ahead and zap them with the fly swatter or capture them in a jar and release them back outside—just to prevent any surprise stings.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service. The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
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