Horsehair worms or “Gordian Worms” find their way into small bodies of water by way of other insects. They do not hitch rides on insects’ skin, wings or other areas of the body. The horsehair worm actually uses the inside of the insect’s body for transportation, among other things. Ew, right?

Also called Cabbagehair, ,Gordiacea, and Gordiid the horse hair worm is a parasite that lives inside crickets, cockroaches, grasshoppers, beetles, katydids, and other anthropod pests. Fortunately, these lengthy creatures prefer not to set up shop inside of animals, humans, livestock, or plants.

Horsehair worms can grow up to 3.2 feet (one meter) and only 0.03 inches (3 millimeters) in diameter, which is about as wide as a kite string. The life cycle begins when a male and female horsehair worm mate in soil or freshwater. The female can lay as many as 10 million eggs. She typically lays her eggs in water plants. Once the eggs hatch into larvae, they live inside cysts in vegetation — vegetation that is ingested by crickets, grasshoppers and other insects or bugs.

Once ingested, the cysts dissolve inside of the grasshopper or cricket gut. The parasite makes its way into the body cavity of the insect where it absorbs nutrients from the insects’ food through the body wall. The horsehair worm is so thin that it can develop and grow to its maximum length inside the body cavity of small cricket. However, the usual length of time that a horsehair worm will develop inside the host is 4-20 weeks.

Amazingly, once the horsehair worm reaches maturity inside of the host, it can live out the rest of its life from the nutrients and energy obtained from the host. Another amazing thing about the horsehair worm is its ability to manipulate its body into many forms. The horsehair worm can even twist itself into a ball that resembles a Gordian knot, hence the name, Gordian Worm.

When the horsehair worm is ready to exit its host, usually when the host is near or in water, it will wiggle out of the nearest opening. They have been spotted emerging from a cricket in the toilet after the insect has been dumped there, and they have even been spotted in pet’s water bowls. They can also be found swimming around in lakes, rivers, streams, garden ponds, and of course, swimming pools.

Although it is more common to find horsehair worms in bodies of water such as swimming pools and streams, this is not always the case. They have also been known to exit on dry land. If you crush an insect on your kitchen floor, the horsehair will emerge in a frantic search for a new host – one he is not likely to find. Once the horsehair worm exits the body of an insect, if it does not find another host, this emerging actually completes the life cycle. If you dare, you can witness the horsehair worm exiting the body of a cricket here. Warning: this is not a pretty sight.

How to Get Rid of Horsehair Worms

Horsehair worms can only parasitize suitable insect hosts, so after crushing pests such as crickets, millipedes, or centipedes, the worms will quickly exit the body and crawl for cover. Unless you kill them right after exiting the body, they will parasitize another insect. That said, because they are not harmful to humans and because they actually kill harmful pests such as grasshoppers, crickets, cockroaches, beetles, millipedes, centipedes, snails, slugs, etc., no control measures are recommended.

If you have a horsehair worm problem, you can:

• Use plain water to get rid of them (you can spray them)
• Install a mesh filter or screen to keep the worms from water pumped from a surface supply such as a farm pond or canal
• Treat domestic water supply systems by filtering and treating with chemicals under the direction of the local health department

To keep parasitized insects out of your home, you should caulk or seal entry sites. If you kill an insect, make sure you take it out of the home immediately. If you flush it, the horsehair worm will escape from the insect’s body through the toilet. You can also place an insecticide barrier around your house foundation to kill any arthropod pests infested with horsehair worms.