50 Nebraskaland • July 2021
MIXED BAG
Invasive species can come in many shapes and sizes.
Often, when we think of invasive species, we imagine
beetles attacking trees, or plants clogging our waterways.
Sometimes, though, the invasive species may be right under
our feet.
Two such invasive species are the crazy worm and the
hammerhead worm. Crazy worms (Amynthas species and
Metaphire species), also known as Asian jumping worms,
are native to east Asia, but have been reported across
much of North America over the past several years. These
worms look like typical earthworms, and are brownish,
grayish or reddish. One identification characteristic is the
clitellium, the cloudy white band found on mature worms.
The clitellium on crazy worms is flush with the body (not
raised up as with other worms) and completely encircles the
worm. Crazy worms also can be identified by their behavior –
they will thrash their bodies wildly when disturbed.
Crazy worms overwinter as immatures in cocoons, emerge
in the spring, and reach maturing by mid-summer. They
consume the organic matter in the soil, changing the soil
structure. This can affect native plant health and reduce
plant diversity.
The hammerhead worm (Bipalium species) is a flatworm
that has likely been in the U.S. for more than 100 years. At
least four species of hammerhead worms have been reported
across the U.S. Hammerhead worms can be gray, brown or
even green in color, and their length can vary from 1.5–12
inches depending on species. The distinctive characteristic
of these worms is their flattened, spade-shaped head.
Hammerhead worms reproduce both sexually and
asexually. If a hammerhead worm is cut in two, or the tail
breaks off, both segments have the potential to regenerate
a full body.
Hammerhead worms are predatory, live at the soil
surface in leaf litter, and feed at night. They will snack
on earthworms, insects, and even snails and slugs. Some
hammerhead worms can produce a neurotoxin so handling
them is not advised.
Report possible sightings of these invasive worms in
Nebraska to the Nebraska Invasive Species Program at
neinvasives.com.
SOMETHING SQUIRMY?
By Julie Van Meter, State Entomologist
Nebraska Department of Agriculture
Left: Crazy worms. Right: Hammerhead worm
JODY GREEN, UNL EXTENSION
