A worm of about 12-inches was found on this woman’s lawn in North-East Louisiana. No photographs were provided, but our reader states that the long worm was “thread-size” and black. She adds that she has never seen a worm like this before.
Despite not receiving any photographs and little context, we still have a decent idea of what the worm our reader found might be. Given its length, girth and color, we would suppose that this was a horsehair worm. The horsehair worm gets its name from a myth that these worms formed in the manes of horses and fell into water as the horse bent down to drink. Obviously, there is no truth to this myth, nor any biological logic, but the worms do nonetheless resemble strands of black hair. Fun fact: these worms are also known as Gordian worms because of their tendency to wrap themselves up into complicated knots, this also being a reference to a myth, this one originating from the ancient Greek myths about the Gordian knot.
Horsehair worms are parasites of various insects such as grasshoppers, cockroaches and some species of beetles, but are not harmful toward humans or mammals. Considered marine worms, these nematode-like worms lay their eggs in water. Once hatched, the microscopic larvae are unknowingly consumed by an insect, who then becomes host to the horsehair worm. Inside the body of its host does the horsehair worm then develop, until finally it breaks free from its host, literally bursting out of the body of the insect and killing it to then swim freely in whatever body of water it can find. What is interesting is that it is still unclear what happens during the larval stage of a horsehair worm’s life cycle. It is thought that they form a protective cyst around their body, which only dissolves once the larva has been consumed by its future host. Upon being consumed, the worm can then leave the protective cyst to wedge itself into the walls of flesh of the host’s gut to start the process of maturation.
In conclusion, we think the worm our reader found on her lawn is a horsehair worm. These worms are completely harmless toward humans, so our reader needs not fear for her health or safety. Their presence is merely an indicator that one of the insects they commonly host has died there, although they most typically choose to eject themselves from their host when they detect that it is near water. If our reader should have more questions about the worm she found, or if she wishes to send in pictures, she may feel free to contact us again.