Bug Blog

The Horsehair Worm: The Parasite That Grows In Insects

The Horsehair Worm: The Parasite That Grows In Insects

We have all heard about parasites invading the human body, but nobody suspects that insects have to deal with the same parasitic inconveniences. After all, insects seem too small to possess any parasitic worms, unless, of course, the parasitic worm is microscopic. Also, insects have been around for millions of years, and they are among earth’s most successful animals when it comes to survival. Therefore it seems improbable that their lives could be endangered by parasitic worms. This is why the horsehair worm are so interesting. Very few people have heard of this arthropod invading parasitic worm. Even more surprising is the size of the horsehair worm. These parasitic worms measure between four and forteen inches in length. Luckily, horsehair worms do not use humans as hosts.

Horsehair worms are long and clearly visible roundworms. They are often spotted by humans in small portions of outdoor and indoor water sources, such as birdbaths, water troughs, pet dishes, sinks, bathtubs, and unfortunately, toilets. These frightening looking parasites can also be spotted in gardens and yards following heavy rainfall. These parasitic worms get their name on account of their resemblance to long threads of horsehair.

For those of you who cannot stand insects, then you will be pleased to know that horsehair worms are only parasitic to larger sized insects, such as crickets, grasshoppers, cockroaches, beetles and katydids. These parasitic worms evolved within the body cavities of these insects. The worms are even harmless to plants, and all types of animals besides insects. In fact, horsehair worms do not pose any threat to the environment at all; it could even be said that these parasitic worms do the world a favor by minimizing cricket populations, and many insect pests. In rare cases when this parasitic insect is found, there is no need for alarm, and control efforts are entirely unnecessary. Lets just hope one of these large parasitic worms does not somehow wind-up in your toilet.


Have you ever spotted what you believe may have been a horsehair worm? If so, where was it located?