Gray Worm in Texas May be an Underdeveloped New Guinea Flatworm

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A reader in Texas recently sent in this image of a worm she found on a dead twig in the dirt after rain. The worm appears to be black/gray in color, and extremely tiny.

Firstly, we want to thank our reader for providing this photograph of excellent quality, taken with a macro lens. Normally, this would make it far easier for us to identify the creature, but, in this case, the worm is so tiny that we cannot help but assume that it is at an undeveloped stage. Secondly, it is the creature’s size and lack of distinguishable features that makes this worm difficult to identify. Despite its gradient of color, its body moving from a lighter, transparent gray to a deeper, less opaque gray, this worm is virtually smooth throughout its entire body. In fact, our reader said herself that the creature did not have legs, nor a visible head. The reader and her mother made several guesses as to what the creature might be, ruling out snails and slugs, and guessing that it might be a flatworm. According to our reader, the worm wriggles like a caterpillar or leech when it stands up. Besides this, the only unique quality she mentioned of the worm was its ability to “make itself thicker and skinnier.”

Taking into account this fact, as well as its appearance and where it was found, we might make an educated guess and say that it is an underdeveloped New Guinea flatworm (Platydemus manokwari). When fully grown, New Guinea flatworms are black and/or gray in color (usually with a faint yellow stripe down the middle of its back), with a cream-colored underside similar to a slug (see image from the web below). Their heads are somewhat hammer-shaped, and their bodies are not round, but rather flat, thus giving them their name. These creatures are native to New Guinea, an island north of Australia, but have become an invasive species in Florida, Texas, and Puerto Rico.

Unfortunately, this worm has gotten a lousy reputation since its discovery in the U.S. Although we can understand that invasive species threaten biodiversity, as it upsets the natural food chain (especially this worm which is predatory in nature), there are other falsely applied labels that have rendered people needlessly fearful of this critter. When researching this worm at first glance, warnings will turn up for this “dangerous” worm that carries life-threatening parasites that everyone and their mothers should be worried about. Some websites even suggest calling 911. It is true that this creature can carry a parasite known as the ‘rat lungworm parasite’, which can cause meningitis (which can be lethal). However, in order for the worm to transmit this parasite, one must ingest the worm itself. Hence, actually contracting the rat lungworm parasite from a New Guinea parasite is nearly impossible, unless one decided to eat one, for whatever reason. However, we do recognize that if our reader has a pet or young child that tends to eat things in the garden, then they could indeed be put in harms way.

Additionally, according to the Florida Fish and Wildlife Conservation Commission (FWC), slugs, frogs and even freshwater shrimp also have the potential to carry the parasite. This demonstrates that this is not a new phenomenon, and the stigma against this worm is unfounded. The only unique threat that New Guinea flatworms pose to humans is their ability to secrete toxins through their stomachs which could potentially trigger an allergic reaction. For that reason, we advise that our reader wears gardening gloves if she comes across one of these creatures when fully grown. However, although our reader did not report any allergic symptoms after handling the worm with her bare hands, as seen in the image, we recommend wearing gardening gloves when handling this worm at any stage. We do want to stress that we are not positive that this is a New Guinea flatworm. It could very well be something else, but seeing as the flatworm has become prevalent in Texas, as well as in the other aforementioned locations, we feel that the information provided could still be of use to our readers.

Now, how does one deal with the flatworms once discovering them? One way of going about it is doing nothing. There are advantages and disadvantages to this approach. The advantage is that this creature preys upon snails, using its pharynx (see diagram below) to drain their bodies. Snails are common pests that eat one’s plants and can be quite a nuisance when one is trying to grow a garden. Thus, the New Guinea flatworm would take care of this issue for you. However, the disadvantage is that many of the snail species it feeds on are endangered species, and regardless of their ‘pest status’, snails are important to the ecosystem. Contributing to the extinction of a species is probably not the best way of going about things. Plus, if one does have pets or small children, one will not want to keep these flatworms around.

Another approach is the use of hot water. According to the FWC, if one soaks soil with hot water which is between 109-120° Fahrenheit, it will kill any flatworms that reside in the soil. Although we seldom condone killing any worm, we think this is an exception. Simply moving these flatworms to another location will not suffice. New Guinea flatworms are nocturnal, so one is not likely to find them during the day, and if one does, it would only be a fraction of the amount that could be hiding underneath the soil. Chron has stated that after testing for samples of the worm in solely one backyard, the Texas Invasive Species Institute (TISI) came away with 50 samples after only two days. Thus, while these flatworms may only pose a mild threat to humans, infestations of them can still occur and they should be dealt with immediately.

To conclude, the worm our reader found on a twig in Texas may be a ‘baby’ New Guinea flatworm, although we are not sure given its modest size and lack of identifiable features. While our reader should not fear this creature being a danger to her, or other adult humans in her vicinity, they can pose a threat toward pets and babies, and can infest one’s backyard/garden. Thus, this flatworm should be handled with haste. If our reader feels ill-equipped to deal with something of this magnitude, we encourage her to seek professional help.


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Gray Worm in Texas May be an Underdeveloped New Guinea Flatworm
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Gray Worm in Texas May be an Underdeveloped New Guinea Flatworm
A reader in Texas recently sent in this image of a worm she found on a dead twig in the dirt after rain. The worm appears to be black/gray in color, and extremely tiny.

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Author: Worm Researcher Anton

1 thought on “Gray Worm in Texas May be an Underdeveloped New Guinea Flatworm

  1. I have been finding these all over my porch , during the day I’ve found over a 100 , iv been putting salt on them . I don’t understand why they are coming out during the day though.

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