One of our readers recently reached out from Florida. He wrote, “I found these worms on my patio after a heavy rain. Most were singular, but there were also clumps of them. I have never seen them before. The patio borders our lawn, where there are patches of mud if that is at all relevant.” The first photo shows a clump of these organisms on the patio:
While adult horsehair worms are free-living organisms, at immature stages they are parasites. Young horsehair worms develop inside the bodies of arthropods such as crickets, grasshoppers, cockroaches, beetles, and other insects. When the horsehair worm is fully developed, it ejects itself from its host body, killing the host in the process. Horsehair worms need a moist environment to survive, so they wait until their host is in or near a body of water to leave its body. Large masses of horsehair worms are most often found after heavy rains, as our reader has witnessed.
Although horsehair worms are considered parasites when it comes to arthropods, they are not dangerous towards humans, domestic animals, or plants. Therefore, no control measures are needed in order to manage horsehair worms. If our reader wants to get these worms off his patio, he can try washing them off the patio and into the neighboring lawn using a hose, or sweeping them away using a broom! Either way, he should know that horsehair worms are generally considered to be beneficial to the environment and not a pest species!
To wrap up, we believe the dozens of white worms our reader found on his patio are horsehair worms. These worms are often found in large groups after heavy rains! Since they are not dangerous or thought of as pests, our reader doesn’t need to worry about them!