Hammerheads in your Garden?

Are there Hammerheads in your Garden?

Called to “come and look at this!” at a friend’s house in Durban, there was this long, thin black looking worm with a distinctive hammer head, slithering and sliming its way across the bathroom floor.

Eeuw!  What on earth is this?   Well, it seems that this is a flatworm that is native to Asia. However, it spreads all over the world, often carried in pot plants.

If you, like me, are totally unfamiliar with hammerhead worms, here is a little background. Hammerhead worms are flatworms and can grow to be quite large, up to 50 centimetres in length, in fact. They are nocturnal, so it is easiest to find them at night, but they are commonly seen in the morning too. They are most often found on the top of soil – like in a garden or on one’s lawn – after it has rained. Like earthworms, hammerhead worms live in the soil because they need a moist environment to survive – and are therefore more likely to thrive in warm, humid climes.  They also leave a slime trail behind them, like slugs and snails.

Hammerhead worm - Bipalium kewense

In a nutshell, here are the basic facts about the hammerhead worm:-

– Half-moon shaped head
– Mouth also serves as anus
– All individuals are hermaphroditic and capable of sexual and asexual reproduction. They usually reproduce by chipping a small part of the tail
– It is considered a pest to farmers because they predate on earthworms
– Non-parasitic, harmless to humans
– Along with the closely related B adventitium, the only known terrestrial invertebrate to produce the Tetrodotoxin toxin

Hammerhead worms are not harmful to humans, nor are they harmful to household pets but they are extremely harmful to earthworms, which they eat. Hammerhead worms will follow an earthworm’s trail to capture it, and then it holds its victim in place with its muscles and a sticky secretion. They then eat the earthworm in the most gruesome of ways. It will push its pharynx out of its mouth and then secrete enzymes on the worm. The enzymes will dissolve the earthworm’s body, and once this occurs, the hammerhead worm sucks the liquefied tissue into its body. Because the earthworm is dissolved before being consumed, the hammerhead worm’s digestion process largely occurs outside of its body.

Hammerhead worms are quite pervasive, and in some places problematically so. Several are considered invasive species and they are capable of depleting earthworm populations.

Earthworms are the most important creatures on earth as they play an important part in fertilizing the soil by excreting tons of castings (excrement) each year, which is a powerful fertilizer.

These facts from the USA – 25 earthworms per square foot of soil equal 1 million earthworms per acre. In healthy soil, 40 tons of castings per acre pass through earthworms’ bodies daily. A new study suggests that there are 1.5 million worms per acre, which move 20 tons of earth each year.

Earthworms also burrow into the soil creating passageways for oxygen and water and are important to the survival of the earth’s plants, trees, and crops

Could it be useful?

Could this worm eating invader be used for fishing bait?

First, hammerhead worms lack natural predators, and this is one reason why they are disturbing ecosystems as invasive species in several parts of the globe. Because of their unpleasant and potentially even toxic body secretions, animals don’t feed on them with any regularity. It follows that aquatic animals might find them distasteful as well. Plus they don’t have a particularly good body texture for fishing. For one thing, their bodies are generally flat and thin – they are acoelomates, which means they have no body cavity – and apparently they break apart easily when being handled, potentially because they try to escape. Flatworms are structurally different from the types of worms that are generally used for fishing, like earthworms, which are in an entirely different phylum (Annelida).  So, sorry, no good to attract fish and of no earthly good to us at all!

So if you see a hammerhead, remember to Save our Earthworms and eradicate this pesky little alien invader immediately!


Remember though, you can’t kill it by cutting it in half, as it will grow into two worms! Just pour salt or vinegar on it to end its life. 

Get rid of hammerheads, one worm at a time.

(It is highly unlikely that you will come across hammerheads of any type at Royal Jozini – as this is dry, pristine bushveld with no introduced exotic plants and an unsuitable climate.)