The Hammerhead worm (Bipalium sp.), also known as Broadhead planarian and landchovy, is a terrifying, toxic terrestrial flatworm. It lives on land and is both a predator and a cannibal.
Hammerhead worms are predators, meaning the worms will feed on other small creatures in the landscape. These include the beneficial and native earthworms. While they are aggressive, the number of hammerhead worms has not reached high enough numbers to impact the earthworm populations yet.
Hammerhead worms are native to tropical and subtropical environments. It is likely they hitchhiked to the United States on the roots of horticultural plants and may continue to be accidentally spread across the country on roots or soil of potted plants. Regardless of how they got here, it appears they are here to stay.Katelyn Kesheimer, an Alabama Extension entomologist
The name Bipalium comes from Latin bi-, “two” + pala, “shovel” or “spade” because species in this genus resemble a pickaxe. They have been found commonly in American greenhouses since 1901. This species is a voracious predator of earthworms and has been identified as a nuisance in the southern USA in earthworm-rearing beds
The hammerhead worm is one of only a very few terrestrial invertebrates known to produce the neurotoxin tetrodotoxin. The worm uses this to immobilize prey and deter predators.
The toxin is also found in pufferfish, the blue-ringed octopus, and rough-skinned newts, but was not known to occur in any species of terrestrial invertebrate prior to its discovery in the hammerhead worm.
University of Georgia agriculture extension agent James Murphy says that the Hammerhead worms have recently been spotted in the state of Georgia. They grow to nearly a foot in length and their mouth is at mid-body.
Do not touch them. Salt is a good killer. Cutting them in half may not be an option as the worms can regenerate. That’s how they reproduce. A small part of the end of the worm will drop off and stay behind and within days, a new head begins to form.
My recommendation is to destroy it by wrapping it in tissue paper, which will dry it out completely. Do not “stomp it”, since severed pieces can sometimes regenerate.Walter Reeves [The Georgia Gardener]
Over time, they were deemed harmless to greenery, but then a more insidious threat appeared. Hammerhead worms have the potential to exterminate earthworm populations. Earthworms are vital because they aerate and fertilize the soil.
Hammerhead worms are considered a threatening invasive species. Some methods used to control slugs also work on flatworms, however, their long-term impact on ecosystems has yet to be fully determined.