What Do Horsehair Worms Eat? Shocking Truth

Horsehair worms enter homes through bathtubs, sinks, and toilets. But what do horsehair worms eat? Are they like pantry pests or something else? Lets find out.

Horsehair worms are parasitic worms that need a host to develop and mature before they begin their life cycle.

While the adult horsehair worms do not have a functioning digestive system, the larvae absorb the nutrients from the skin of their host to grow and survive.

Read on to learn more about these fascinating worms, what they eat and how they live.

What Do Horsehair Worms Eat

Why Is It Called a Horsehair Worm?

Horsehair worms come from the family of Nematomorpha and look similar to nematodes.

However, they are much longer (about 4 inches or more) and found in water bodies, such as ponds, sinks, bathtubs, puddles of rainwater, toilets, and alongside lakes and rivers.

They are referred to as horsehair worms because they are as thin as a horse’s hair.

These curious creatures are often found in a contorted position, which makes them look like a loose ball of thread.

They also look like Gordian knots, named after the Greek legend that the King Gordius of Phrygia used to tie intricate knots.

Horsehair worms are parasitic but are harmless to humans, plants, and animals. They mature in the body cavity of host insects.

What Do Horsehair Worms Eat?

The primary purpose of adult horsehair worms is reproduction before they die. So, their digestive system doesn’t function, and thus, they do not feed anything but lay eggs in freshwater.

The horsehair worm larvae, however, grow and develop by consuming the nutrients from the body of its host. It absorbs the nutrients from the skin of the host.

There are more than 300 species of horsehair worms, and each has a preference for a different potential host, including grasshoppers, cockroaches, centipedes, crickets, and more.

Where Do They Live?

You can find adult horsehair worms freely living alongside water bodies and aquatic environments, such as puddles, pools, ponds, lakes, marshes, streams, etc.

Some can also be found in your home – sink, bathtub, toilet, garden, etc. On the other hand, horsehair worm larvae develop and mature in the body of the terrestrial host.

Once it has grown completely, and the minute its host gets close to a water source, the larvae get out by crushing their body.

They then live out their days in the water, laying eggs and restarting the cycle of life.

What is their Lifecycle Like?

The lifecycle of this worm is quite interesting. It starts with adult horsehair worms mating. They mate in groups and tie tight knots during the activity.

Once the mating season ends, the male worm dies.

Then, the female horsehair worms lay millions of eggs in a freshwater source. She may release the eggs in small sections, together, or in different groups.

Once she releases the eggs, the female dies. It takes about two to three weeks for the egg to hatch, and once it does, the cylindrical larvae enter its host’s body.

It can enter either directly with barb-like hooks or encyst on aquatic plants or vegetation, which the host eats.

They can also enter an intermediate host, like the larvae of an insect, and stay with it until it pupates, gets out of its cocoon, and eventually dies.

Horsehair Worm

After entering the host’s body, the larvae start absorbing nutrients from its skin to mature within a few weeks or months.

After it fully develops, the larvae crush or break through the host’s body to start their life cycle. Many larvae chemically infect the brains of their host, which drives them to seek a nearby water source.

When it reaches the head, the adult juvenile worm finds an opportunity to crush its body and get out.

How Do Their Larvae Parasitize Other Insects?

It begins when these worms mate. Once the mating season ends, the female heads into a freshwater body to lay millions of eggs.

The eggs take about two to three weeks to hatch, and once they do, the larvae wait to enter inside an insect, like a cricket, which might take them in as they drink water.

The larvae can also encyst on aquatic vegetation and get eaten by the larvae of another insect.

Once the larvae grow into an adult, they might get eaten by another insect, like a midge or mosquito, and the horsehair worm ends up in its desired host’s body.

Once they are in, the larvae penetrate through the gut to reach the host’s body cavity. It absorbs the host’s nutrients until it develops into a foot-long adult.

It then infects the host’s mind to kamikaze into a water body, and the minute it does, the worms break out of the body, eventually killing it.

Frequently Asked Questions

What does a horsehair worm do?

An adult horsehair worm mates and lays millions of eggs in freshwater bodies. Since it is parasitic, the larvae enter the body of a potential host and mature for the next few weeks.
They then wait for the host to reach a water source. At this point, they jump out, crushing behind the host and restart their cycle of life.

Do horsehair worms need water?

Horsehair worms need water to lay eggs, enter the host’s body, and continue their life cycle.
So, yes, horsehair worms need water for their survival. You can find them in streams, rivers, lakes, puddles, marshes, and even in your bathtub and sink.
These bugs cannot survive water in the adult stage of their lives.

What do horsehair snakes eat?

The horsehair snake is an internal parasite that absorbs the nutrients from the body of its host until it matures completely.
Adult horsehair worms, however, have a non-functioning digestive system, so they eat nothing throughout their life cycle.

Do horsehair worms lay eggs?

Yes, the female horsehair worms lay millions of eggs in a freshwater body. Once she lays the eggs, the female dies.
The larvae, then, find a host to grow and mature, after which it bores out of the host’s body to start their life cycle.

Wrap Up

Horsehair worms are intriguing creatures that do not need much to survive apart from killing a host! They eat the body of the host and leave it a hollow shell.

They then force the host to go to a body of water, jump out, and leave the dead host behind.

We hope this article helped you learn all you should know about the diet of horsehair worms. Thank you for reading!

Reader Emails

Many of our readers have emailed pics of this thread like worm, asking us to identify it and let them know if it is harmful or not.

If you watch the photos below, you will realize why most people are terrified of this bug. Do read and get a better perspective of them. Thankfully, these worms are not very dangerous to humans.

Letter 1 – Horsehair Worm parasitizes Potato Bug


Potato Bug with something that busted out of it.
We found this Potato Bug on the floor in our studios, still moving. At first I thought the long black thing was intestines. When I scooped it up with a paper towel the long black then fell to the ground and moved rapidly. It appears to be a worm of some sort. How it came from this bug and what type of parasite or worm it is is not known. At first I thought someone must have accidentally stepped on the bug, but on closer examination, it appears the worm busted out of the bug. Have you seen anything like this?
Robbie Rush

Hi Robbie,
We have heard several stories about Potato Bugs being parasitized by Horsehair Worms. Dr. Bug substantiates that Horsehair Worms in the genus Gordius are Potato Bug parasites. Here is a quote from his site: “They are sometimes found dead in swimming pools and ponded waters. This is either the result of a simple drowning or a parasite infection. The horsehair worm (Gordius spp. or Paragordius spp.) can inhabit the jerusalem cricket’s gut and feed. The worm can alter the behavior of the cricket and force it to seek water. Once in water, the worm bursts through the insect’s abdomen and seeks a mate. The cricket dies from the wound. I have found them in ponds at O’Neill Regional Park in Trabuco Canyon (1980’s) and at Starr Ranch Audubon Sanctuary (2002).”

Letter 2 – Food Chain: Parasitic Horsehair Worm and Potato Bug prey


Potato Bug and Gordian Worm Location: Porter Ranch, California February 12, 2011 8:40 pm Hello Bugman! I spotted this Jerusalem Cricket in the pool this morning (02-12-11), although I had no idea what it was at the time. After I scooped it out and realized it had drowned, I then spotted what I thought was an extremely skinny snake swimming in the pool. I scooped it out also, then took a few photos of the ”snake” and the ”termite on steroids”. I threw the ”snake” over the fence and went inside to get a ruler for size in the photo of the other bug. I wasn’t quick enough because a Scrub Jay spotted him and flew off with lunch before I could take photos with a ruler. Frustrated, I decided to begin at What’s That Bug and Bugguide.net to identify the bug. Little did I know that the ”snake” was actually a Gordian Worm or I’d have taken more care to get a decent photo. Drat. Offering gratitude for your awesome sight, although photo perusal did cause me several shivers and a couple of gags. (I like bugs for the services they provide and their place in the world, but it does get a bit creepy to look at their anatomy in detailed images. To that end, I’m attaching my own creepy images.) After finding out what the duo were named, I even found a video online showing a cricket dive into a pool and the worm wriggle out of him. *shiver again* (I had four pictures – attached are three) Signature: Regards, Tiffany Hawkins
Jerusalem Cricket
Dear Tiffany, Thank you for your wonderful email and excellent photos.  The relationship between the parasitic Gordian Worm and the host Jerusalem Cricket or Potato Bug is a chilling example of complexity of the web of life on our planet.  The chances of a Jerusalem Cricket ingesting the cyst of the worm and then hosting the internal parasite until being suicidally driven to seek out water in which to drown itself are quite slim, yet enough Gordian Worms survive to perpetuate the species.  Gordian Worms are also known as Horsehair Worms.
Gordian Worm

3 thoughts on “What Do Horsehair Worms Eat? Shocking Truth”

  1. When I was a boy about 10 or 12 I found a Jerusalem Cricket in my yard. I captured it and put it in a bottle. The next day, there was a horsehair worm on the bottle with it. Not knowing anyone who could explain what had happened, we were forced to conclude that the worm was a parasite. Not until now have I ever read anything that confirmed our suspicion. Thank you for your post.

  2. I have seen this with my own eyes! Me and my gf just saw a potato bug and I was telling her a story how I accidentally smashed a potato bug and a long hair like worm was living inside it’s butt!


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