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A Closer Look: Giant Moths of North Dakota


Chris Grondahl

Jpg-Polyphemus moth
An adult polyphemus moth is similar in size and appearance to the cecropia but lacks the orange-red coloration. It also contains eye spots outlined by yellow. This moth is found in wooded areas around the state.

Originally published in:
North Dakota Outdoors
(July, 1996)

Official publication of the
State Game and Fish Department
100 North Bismarck Expressway
Bismarck, North Dakota 58501-5095

This resource is based on the following source:
Grondahl, Chris.  1996.  A closer look:  A closer look:  Giant moths 
     of North Dakota.  North Dakota Outdoors 59(1):10-11.
This resource should be cited as:
Grondahl, Chris.  1996.  A closer look:  A closer look:  Giant moths 
     of North Dakota.  North Dakota Outdoors 59(1):10-11.  Jamestown, 
     ND: Northern Prairie Wildlife Research Center Online.
     (Version 15MAY98).

Return to A Closer Look Series
Saturniids, or silk moths, are the largest moths in North Dakota.

Of the 1,200 species of giant silk moths in the family Saturniidae, 68 of these occur in North America and nine are found within North Dakota.

The smallest silk moth has a wingspan of about an inch, while the largest, a species from Asia, has a wingspan of near 10 inches.

Silk moth cocoons are actually spun from real silk. Some species are raised solely for production of that fine fabric. Silk production in the Orient has actually advanced to the point where silk moths are hybridized to spin different colors of silk including yellow, white and pale shades of purple and red.

Many silk moths in North Dakota form a cocoon with either too much glue or with a fabric meshwork too tightly woven to enable harvest of silk material.

Three subfamilies of Saturniidae are represented by the nine species of moths found in North Dakota. They are the Glovers silk moth, cecropia moth, polyphemus moth, luna moth, Io moth, Nevada buck moth, sheep moth, Pandora's moth and Manitoba oak moth. Since caterpillars of these species all feed on trees, they are primarily restricted to wooded areas including river and stream corridors, the Turtle Mountains and Pembina Hills, and other densely wooded regions.

Each moth species' caterpillar has a favored plant host upon which it feeds. Knowing these specifics can help you key in on the right plant if you are in search of a certain species. For instance, Dr. Gerald Fauske, entomologist at North Dakota State University, said that one year they found hoards of Pandora's moth near the Burning Coal Vein campground in western North Dakota. Why? Because the caterpillar feeds on ponderosa pine common to the area.

The cecropia moth is a little less specific in its plant choices, which include plum, apple and willow species. It is found primarily in the eastern half of North Dakota. Another species, polyphemus, is found statewide in association with oak or maple. Both these large silk moths can be found in June and early July.

Jpg-Cecropia moth
An adult cecropia moth has emerged for its short life span to attract a mate, reproduce, and die. The cecropia is found in wooded area in the eastern half of North Dakota.

Cecropia and polyphemus begin as an egg produced by a female moth. The female moth disperses a billionth of a gram per hour of a scent called a pheromone. This attracts a male moth from as far as 150 yards away. He has an elaborate furry antennae with sophisticated olfactory sensors that sift the air for the female's scent. Each antennae has approximately 1,700 hairs and each hair has 2,600 olfactory pores. The hairs work to concentrate the pheromone at a million times the level in the air itself, thus producing a rather strong "smell" to the male. The scent is so potent in the insect world that some spiders have learned to mimic a moth pheromone to lure an unsuspecting moth victim into their web.

After mating, adult moths immediately die. Eggs later hatch into caterpillars that feed a month or two, reach maturity, then spin a cocoon in which they spend the winter. These silk cocoons vary enough in shape and color to be used as a tool to identify the species that made them. In the spring, when warm temperatures return, adults emerge from the cocoon and the cycle continues.

Jpg-Cecropia cocoon
A cecropia cocoon attached to twigs will stay in place until spring. Warm weather triggers the evolution of a new moth. Cocoons can also be used to identify each species since they differ in shape and color.

Moths have a special place in the web of life. These insects are important pollinators of plants and their caterpillars are a primary food source for songbirds. They are also eaten by everything from the smallest mammal - the shrew, to one of the largest - the grizzly bear.

As a general rule, moths fly by night and butterflies fly by day. Butterflies depend on their bright colors to tell birds they have eaten plant toxins and therefore taste bad. Night-flying moths don't have this worry except for an occasional bat looking for a meal.

Moths disguise themselves as dead leaves, lichen and bark during the day. Butterflies perch with their wings up and have club-like knobs on their antennae tips. Moth antennae look more like feathers and they perch with their wings outspread.

Jpg-Cecropia caterpillar
A mature cecropia caterpillar crawls in search of its favorite vegetation during the summer months. Caterpillars of silk moth species feed one to two months before they spin a cocoon that will keep them covered durng the long winter. Caterpillars can be identified as to what moth species they will become.

A common misconception about moths is that they are attracted to light. Moths actually attempt to avoid light by flying toward the perceived dark area to the edge of the light. They get confused and spiral into the light itself. Once they are there, they cannot figure an escape route and are often found by collectors in those situations. Mankind's spread of illumination during the night, collecting, pesticides and habitat loss have combined to make moths less common than their biology would dictate.

A good source of information about moths in North Dakota is "Butterflies and Moths" by Herbert S. Zim. Dr. Fauske is an expert on these creatures in North Dakota and is also in the process of publishing a book on his work in the state. If you have any questions, please call Chris Grondahl at 328-6612.

Chris D. Grondahl is a biologist with the Department's natural resources division, and coordinator of the Nongame Wildlife Program.

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