A reader recently sent us this short message, “Are these horsehair worms? Many seen on the cement bike trails at the Wylie Prairie, Wylie, TX after a heavy night of rain. The one in the picture was about 12 inches long.” The photograph shows three thin worms on cement:
We agree with our reader… these are horsehair worms! Horsehair worms are very thin and long, often comparable in appearance to angel hair pasta or a piece of hair (hence the name.) They are almost always found in or near water. While our reader didn’t find these worms in a pond or bucket, he did mention that it rained heavily the night before, so the worms might have been washed out of a nearby body of water and onto the bike path.
Horsehair worms begin as parasites. They develop in the bodies of arthropods until they reach maturity. When the host goes near or enters into a body of water, the horsehair worm ejects itself from the host and into the water. Unfortunately, the host always dies in the ejection process. Common arthropod hosts are cockroaches, grasshoppers, beetles, and crickets. When horsehair worms first eject themselves they are white, but their color soon changes to a dark brown.
We don’t know if these horsehair worms left their hosts during the heavy rain, or if they were already free-living, and simply moved onto the bike path during the rain. Our reader doesn’t need to stress about coming into contact with these specimens because they aren’t parasitic to anything other than arthropods, and only during their larval stage. If he wants, he can even move them off the bike path and into a nearby puddle to prevent them from being run over!
To wrap up, we believe the worms our reader noticed on the ground during his bike ride are horsehair worms! These worms need a wet environment to survive, so it is no surprise he noticed them after a heavy rain.