Scientific name: Lymantria dispar
Native range: southern Europe, northern Africa, central and southern Asia, Japan
Gypsy moth is regulated in Minnesota. Lake and Cook Counties are under quarantine. See Minnesota's Gypsy Moth Quarantine.
Gypsy moth was introduced to the United States and Canada in 1869, and has since spread across much of the northeastern U.S. See the history of gypsy moth in the U.S. and Minnesota.
Gypsy moth is a notoriously destructive insect, which feeds on the leaves of hundreds of species of plants.
Gypsy moth undergoes four life stages: egg, caterpillar (larva), pupa, and adult.
Eggs are laid in a fuzzy, tan-colored mass. The egg mass contains 500-1,000 eggs and is about the size of a quarter. Eggs are laid during late summer and hatch the following spring when the weather is right. Egg masses can be found on living and/or inanimate objects, including nursery stock, logs, roof eaves, in wheel wells or outdoor household articles like firewood and lawn chairs.
The caterpillar hatches from the egg and grows to a length of 2½ inches as it matures. Its body is covered with hairs to protect it from predators including curious humans. Be careful - if you touch it your skin might get irritated! Along its back the caterpillar has five pairs of blue spots near the head, followed by six pairs of red spots. It actively feeds on plant foliage from late spring through mid-summer, when it develops into a pupa.
The pupa is an immobile stage of this insect's life. Though it appears inactive, it is very busy inside transforming from a caterpillar into an adult moth. Found mid-summer, it is dark reddish-brown, leathery in appearance, and often tethered to an object with silk strands. It can range in size from ¾ inch to 1½ inches long.
The adult female moth is white with brown jagged markings on her wings. Her wingspread ranges from 1 to 2 inches but she cannot fly because her body is so large and heavy with eggs. She releases a pungent sex attractant (pheromone) that only the male moths can smell so they can fly to her and mate. The female produces one egg mass and dies.
The adult male moth has feathery (plumed) antennae that are so sensitive they can "smell" a female a mile away. His body can be light beige to dark brown with black jagged bands on brown forewings. His wingspread ranges from only ¾ to 1½ inches yet he is a strong flyer and capable of mating with several females. Adult moths are typically active from late summer through early fall.
This chart shows the average developmental times for gypsy moth in Minnesota. The length of each life stage depends on weather conditions, which vary annually.
It is still rare to find gypsy moth in Minnesota. Usually the only way they are detected is when lured into survey traps that MDA field staff and other cooperators place throughout the state. Other species that are much more commonly found in Minnesota such as the Forest and Eastern Tent Caterpillars can be similar-looking to gypsy moth. Their defoliating larvae can also be pests, but they are not federally regulated pests like gypsy moth is.
If you think you may have found gypsy moth, compare it first to the similar moths and caterpillars pictured below. If still in doubt, take a digital photo and email it to firstname.lastname@example.org, or call the Arrest the Pest Line at 1-888-545-MOTH.
Gypsy Moth caterpillars have very distinct markings: 6 pairs of red dots, 5 pairs of blue dots.
Gypsy moth caterpillar
As animals and plants interact with each other over millennia, they develop mechanisms to increase their chances of survival. For example, the gypsy moth caterpillar is so hairy that birds and rodents think twice about eating it as they may end up with irritated skin around their eyes and mouths. Nevertheless, some predators will take that risk in order to have a bite to eat.
Another example is the behavior of the moth. The caterpillars are most active at night, dining on leaves by moonlight. They rest in a sheltered area during the day to avoid being attacked by birds.
Birds are just one problem though. The white-footed mouse is a rodent that eats gypsy moth caterpillars and pupae on and near the ground while they are resting. Mouse predation may be a very important factor in keeping small gypsy moth populations from getting bigger.
Smaller enemies include a number of tiny parasitic wasps and flies whose larvae feed on gypsy moth eggs or caterpillars. The adult female protects her eggs from predators by wrapping them in a mat of tiny hairs from her own body. Some of these small insects have been put into service by scientists trying to find a way to control large populations of gypsy moth.
On a microscopic level, a fungal pathogen called Entomophaga maimaiga has been studied and found to provide significant control of gypsy moth outbreaks. Wet conditions during springtime encourage the natural growth of the fungus. Spores from the fungus must be ingested by the caterpillar. Once inside, the spores start growing and eventually kill the caterpillar.
Gypsy moths are susceptible to a virus called NPV. When there are high numbers of caterpillars very close to each other, the virus is easily passed along. The caterpillars get sick and die very quickly, and some outbreaks have been virtually eliminated after NPV is introduced. NPV has been mass produced for control of gypsy moth and is sold under the brand name Gypcheck.
Contact the Minnesota Department of Agriculture via Arrest the Pest or by sending an email to email@example.com if you suspect you have found gypsy moth.
Minnesota Department of Natural Resources
Gypsy Moth or Forest Tent Caterpillar?
Forest Tent Caterpillars
New York State Department of Environmental Conservation
Caterpillar Comparison Chart
University of Minnesota Extension
Forest Tent Caterpillars
Arrest the Pest
Minnesota Department of Agriculture (MDA), 625 Robert Street N, St. Paul, MN 55155-2538, firstname.lastname@example.org