This photo is courtesy of the Purdue University Landscape Report, as is the text below.
Hammerhead worms, sometimes called shovel-headed garden worms, are a type of land planarian, or flatworm. Flatworms are worm-like organisms that lack the segmentation of earthworms and have the ability to regenerate from parts and pieces. Hammerhead worms belong to a subset of planarians, the genus Bipalium; while there are a few native species of Bipalium, most are from tropical regions. It is believed that hammerhead worms have been present in North America for long time, preferring environments that stay warm and moist through most of the year. Hammerhead worms are named for their spade-shaped head and typically have bright colors with dark lines running the length of their bodies. They are often found in indoor spaces and greenhouses that are temperature controlled and maintain humid conditions. Hammerhead worms can also be found living under rocks, fallen trees, or anywhere that can maintain a high enough relative humidity. While some flatworms are able to live in drier conditions, Bipalium need moisture in order to survive.
Members of Bipalium are predatory, consuming invertebrates like earthworms, snails, slugs, and some soft-bodied insects. Once they capture a prey item, they envelop it in a mouth-like organ located on the underside of their bodies. The primary issue with hammerhead worms is the potential damage they can do by preying on beneficial organisms that maintain soil and plant health. Hammerhead worms, and all other planarians, lack a closed body plan that uses a one-way digest system. Once they eat something, it is digested and waste is excreted through that same mouth-like opening. Some members of Bipalium can also use a toxin called tetrodotoxin to subdue their prey; however, they only produce a small amount and lack a way to use it on a larger organism. While they are often confused for more dangerous species, the Bipalium in North America do not represent a human health concern. Just keep any pets or children away from them, and if found, use gloves if you’re forced to handle them.
As mentioned above, one of the more unique traits of Bipalium, and planarians in general, is their capacity to regenerate new individuals from parts and pieces. A piece as small as 1/279th of the whole can regenerate into a new individual. Do not attempt to chop up or crush hammerhead worms, or you may be dealing with several dozen when new worms develop in two weeks. However, even though it seems like hammerhead worms could reproduce very quickly, it’s still fairly uncommon to see one. If found, place it in a bag or bucket with either salt, alcohol, or vinegar until the worm is dead. As long as you do not cut or chop up the worms, it is very unlikely you’ll have to deal with more than one at any given time. Just keep your eyes open and remember to report any sightings to 1-866-NOEXOTICS!
I doubt I will ever have to deal with this oddball invasive at my current location, thank goodness.
Fall cleanup is winding up - just a few more things to do. I'm getting antsy to plant something - anything! - but I will have to wait. This morning's dog walk required a parka, mittens, and hat. At least the sun is shining and the goldfinch are back.
