What Do Horsehair Worms Eat? Surprising Facts Uncovered

folder_openNematoda, Nematomorpha
comment10 Comments

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

Reader Emails


Letter 1 – Worms


Hi, I found a worm like bug under a rock. Light brown and it stretched out to about sixteen inches. It seems sticky and real skinny. I wanted to know if it was poisonous and wanted to ask you. can you help me find out what it is? :
H.R age 12 thanks

Dear H.R.
We got a letter several weeks ago from a man who described much the same thing as you describe.
He enclosed a headsketch. We identified his "worm" as a Arrow Headed Flatworm, Bipalium kewensis. It is a land planariun and is slender and brown. They have five longitudinal stripes on the body and a head shaped like a hammer. It needs a warm, moist environment and is often found near water spickets. Flatworms are hermaphroditic, and copulation involves mutual insemination; they may also reproduce asexually by fragmentation. They are benign creatures since they do no damage to plants nor do they cause medical problems. Here is our other reader’s sketch, though we lost his wonderful original letter. Hope that is a positive ID for you.

Letter 2 – Worms


I have little worms in my home. They generally appear on the floor; however I have found a few in the bathtub, and one in my bed! It seems that there are more everyday throughout my home, and I cannot find the source of where they are coming from. They look like your average worm that you would find outside after it rains, however they are only about an inch long. They are brownish black, with a black end on one side. One of the larger ones even appeared to maybe have legs like a caterpillar. I know they are not millipedes, centipedes, wax worms, or weevils. I have never seen anything like them before. They started to appear about one month ago, but it seems that there are more each day! They do move around, and seems to travel fairly quickly! They do not have any hair, and they are textured, and look, like a normal worm. Help!

Dear Sheri,
All insects that go through complete metamorphosis have a larval form that could be considered worm-like. Some are more worm-like than others. The real question here is which of these larvae are most likely to be found in the home. My guess is the Mealworm (Tenebrio molitor) the largest of the pantry beetles. The larvae are worm-like, pigmented, and very smooth. They are sometimes sold as fishing bait and as food for pets under the name Li-Cut worms. They and the adults are fond of flour products found in the pantry, but that does not explain how they wandered into the bed. Another suspect could be the larva of the Click Beetle (family Elateradae) which are known as wireworms. The adults are often attracted to lights which will get them into the house, and the larvae live primarily in the soil where they feed on herbaceous plant roots, tubers and stems. Other types of beetles have larvae that bore into wood, like the Nautical Borer (Xylotrechus nauticus) which often appears mysteriously indoors after hitching a ride in firewood. The larva is about 3/4 inch long when mature and pale dirty brown with an enlargement just behind the head. It bores into the heartwood of dead oak and other hardwoods.

Letter 3 – WORMS!


We have a mystery source of a thin worm or bug larvae which seem to appear from nowhere onto a localized part of the kitchen counter near a non-opening window. I couldn’t find the source so in a mad cleaning frenzy I even got into the recessed light fixtures. I found lady bug and other carcasses (ugh!) but no clear indication of the mystery creature. Perhaps if you can identify these guys I could figure out where they are coming from and then destroy the source. The worm/larva is about a half inch in length, very thin, with smooth cream/tan color skin. It has rings around the body which are either a slightly darker color or textured depressions (I was too grossed out to look with a magnifying glass). They appear to be more larvae like rather than "caterpillarish" i.e. no hair or pretty colors. They never appear to be moving when I see them. Fortunately there have been less than a dozen sightings. Any ideas what the heck these things are? Thanks for the help! I enjoyed reading all the letters and answers.
Melody Williamson
Northern Illinois

Before WHAT’S THAT BUG? even had a chance to answer, Melody writes back:

Well, just wanted to let you know that the bugs in question were wax worms. My son (the fisherman) knew them immediately. I called the exterminator and it turns out that the Wax Moth lays eggs in bee and wasp nest! I have a nest in peak in the roof line that is infested with wax worms. Ick!
Thanks for being there!
Melody Williamson

Not to be outdone, WHAT’S THAT BUG? replies:

Dear Melody,
I am happy to hear that you had your bugs identified before we here at What’s That Bug could provide you with misinformation. My first inclination was that you had maggots, which considering the time of year and the heat were my only real suspect. Wax worms (Galleria mellonella) never even entered my mind. When we got your follow-up letter, I checked out an internet search and learned that of all the worms considered for use on the hit television show Fear Factor, wax worms were considered the most maggot-like and 30,000 of them were used in one challenge. Check out this website for more gross information about the wax worm: http://www.nbc.com/Fear_Factor/stunts

Before you get that exterminator, you might want to consider reselling the larvae which are often used as fish food. This website: http://www.armstrongcric
sells 1000 wax worms for $22.

Letter 4 – Worm: Diseased? or unusual species???


Pink Spotted Earthworm?
March 4, 2010
I hope you can help us identify this unusual worm my husband discovered today while trying to photograph a mole! I didn’t see the worm, but he took several photos and after a brief internet search we’re stumped (not that we would expect otherwise, being that we’re *not* experts!). Is it just a regular earthworm with some kind of disease?
North of Houston, Texas, in Montgomery County


Hi Meg,
The worm in your photo is sure crazy looking.  We cannot say if it is diseased or an unusual species without doing research on the matter, and our time at the moment is limited by other obligations.  We hope by posting this quickly, someone will be able to provide us with an answer.


Letter 5 – White Worm from India


White worm ? Reminder )
June 20, 2011 10:20 PM
Thanks a lot for the painstaking efforts for keeping the site authentic.
Here is another one from my place, Kerala India.
This is a white earthworm(?) found near a paddy field in murky waters. It measured almost 32 cm and the girth would be 2 cm.
what would be this ?
Warm regards
Ibrahim TMC
Kasargod- Kerala

White Worm

Dear Ibrahim,
We really love your photo using the umbrella to cast a shadow and eliminate glare.  We have no idea what this White Worm is and we will need to do some research.  We can’t help but to wonder if it spends its life in dark places so it doesn’t need pigmentation.  Our sense of the macabre just kicked in and we can’t help but to wonder if this might be some human parasite.

White Worm

We just had this incredible desire to read Bram Stoker’s Lair of the White Worm, and it seems the entire text is available online.  We like this larger type version even better, though we would much rather read the book.

White Worm

Dear Daniel Sir,
Your efforts were painstaking to identify the white worm.
My friend from the Zoological Survey of India, Calicut is quite sure that it is an earthworm. They call it Dravida Nilamburiansis. Further he informed me that it would measure up to a meter in length.Earlier thought it was endemic to place called Nilambur, in Kerala India.
Warm regards,
Ibrahim TMC

Letter 6 – Unknown Worms on Pumice Bar


Subject: rice like worms in my pumice bar
Location: shower, st Louise missouri
October 11, 2012 8:35 pm
Can you please help me figure out what these are so I can figure out what measures I,need to take to get rid of . I found them in my pumice bar in the shower.
Signature: Charline henry from missouri

Mystery Worms

Ed. Note:  Our automated response:
Thank you for submitting your identification request.
Please understand that we have a very small staff that does this as a labor of love. We cannot answer all submissions (not by a long shot). But we’ll do the best we can!

Im thinking they are larvae from drain fly but I am not for sure

Hi Charline,
There is not enough detail in your photo for us to be certain.  They might be Drain Fly larvae.  They appear to resemble this image from BugGuide.  Perhaps one of our readers will have a better idea what they might be.

That looks like them but they are a little darker. Would they lay eggs in a pumice bar?

They are usually found in the sludge that forms in drains.  The pumice bar location is a real puzzler.

That what has me stumped, unless it got into the liqour before it laid the eggs…. now ive seen some silverfish and my neighbor,we live in condos, said she has had carpet beetles. do u think it could be one of them?

Neither Silverfish nor Carpet Beetle Larvae.

Letter 7 – Small mounds of dirt: Worm Castings or Not???


Hi WTB….we have removed our lawn in the backyard and are in the process
of re-landscaping. Today, I noticed these little mounds of dirt. I seem to
recall that these might be made not by ants, but by bees. These mounds are
everywhere! We are in Eagle Rock…
Hope all is well!
Brenda Rees
Southern California Wildlife

Worm Casings???
Worm Castings???

Hi Brenda,
We do not believe these are caused by Bees.  We suspect they might be Worm Castings.  See Scotty’s Place and  News Times for similar images.  News Times states:  “The little mounds are actually earthworm castings. Recent rains have been helped plants stressed by drought, but more soil moisture and cool temperatures increased earthworm activity” and we did just have a good soaking last week.  The same image is used on Horticulture.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Unknown Striped Flatworm from Singapore is probably Bipalium rauchi


Land Planaria
I came across this planarian during one of my hike up Bukit Timah Hill, Singapore. Any idea what is its name? Sincerely,
Vincent Tan

Hi Vincent,
A cursory search online did not produce any matches for your gaudily striped Flatworm from Singapore. Perhaps one of our readers will have better luck than we have had with the identification. One would think that such distinctive markings would have been noticed and noted.

Update: (07/29/2008) ID for Unknown Striped Flatworm from Singapore
Hi Daniel,
What a gorgeous terrestrial planarian! There is a very nice shot of this same species at: http://www.flickr.com/photos/budak/1148748518/ If the ID there is correct, then this is probably Bipalium rauchi von Graff, 1899. Best,
Susan H.

Hi Susan,
It is so wonderful to be able to post a photo in the morning, then go to work in order to be able to pay the mortgage, endure an earthquake, and then return home to find an identification in the mailbox. Thanks heaps.

Update: (07/29/2008) Unknown Striped Flatworm a P.S.
The generic name now seems to have been changed to Diversibipalium , thus the species would be Diversibipalium rauchi (von Graff, 1899).

Another Reader’s Update: (07/29/2008) Unknown Planarian on your site
You have a picture of an unknown flatworm from Singapore on your page from 7/27/08. I just wanted to throw in my two cents. I saw a similar looking creature on flickr and someone replied leaving a comment saying it was in the genus Bipalium. So, I googled the genus and came across this website: http://www-biol.paisley.ac.uk/biomedia/text/txt_pictures.htm It lists different picture names in alphabetical order. Under Bipalium is a picture that nearly exactly matches the flatworm on your site. The link to the flickr picture: http://www.flickr.com/photos/budak/1148748518/ The third comment lists a possible species level ID as well as a few sources. Don’t know if this is what you’re looking for, but I hope it helps. Thanks,


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

    View all posts
Tags: Horse Hair Worms

Related Posts

10 Comments. Leave new

  • It would appear that the white worm you have seen is spoken about in the ancient text of a greek historian “Philostratus” The Life History of Apollonius, The worm is described in Book 3 chapter 1, “There is also a creature in this river which resembles a white worm. By melting down they make an oil, and from this oil, it appears, there is given off a flame such that nothing but glass can contain it. And this creature may be caught by the king alone, who utilizes it for the capture of cities; for as soon as the fat in question touches the battlements, a fire is kindled which defies all the ordinary means devised by men against combustibles.”
    It is interesting reading, as there is much to be told of India within it.

  • Hello There,
    I’ve found some little things by my sink and I’m just not sure what they are. They are about a half of an inch long, of a dark brownish color, with black stripes, and are very thin. They’re not what I originally thought: centipedes. They are not like any pictures I’ve found of wax worms, centipedes, or meal worms. Most of those things are much thicker.

  • Hello There,
    I’ve found some little things by my sink and I’m just not sure what they are. They are about a half of an inch long, of a dark brownish color, with black stripes, and are very thin. They’re not what I originally thought: centipedes. They are not like any pictures I’ve found of wax worms, centipedes, or meal worms. Most of those things are much thicker.

  • actually my husband came home and told me they are millipedes, just a different type than I’ve seen in books and movies. Thank you so much for helping though.

  • I saw this today in the Pacific NW. It’s definitely diseased. It looked nearly the same as this picture. If you look at your picture closely, you can see some of the white dots are actually blisters. The worm I saw today also was very slimy and sticky. It was with other earthworms, that did not show signs of sickness.

  • Blane E Christensen
    October 17, 2016 8:56 am

    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.

  • 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!


Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed