Plants and Animals

Pachypolia atricornis Three-horned moth

Key Characteristics

This small moth has an average wingspan of 1.7 inches (4.3 cm). The forewing (i.e., upper wing) is gray with a slight olive tint with the median or middle area a little darker. The hind wing (lower wing) is dark gray or brownish gray.

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G3G4 - Rank is uncertain, ranging from vulnerable to apparently secure
State Rank: S1S3


CountyNumber of OccurrencesYear Last Observed
Cheboygan 1 1989
Otsego 1 1970

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


In Michigan, the Three-horned moth is associated with mature beech-maple forest, oak-pine boreal forests, lowland and mesic hardwoods, and lowland and mesic coniferous forests. The host plant for the larvae of this species is unknown at this time but may be a Vaccinium species or other member of the Ericaceae family.

Specific Habitat Needs

Host plant needed in: Dry-mesic northern forestHardwood-conifer swampMesic northern forestNorthern hardwood swampRich conifer swamp.

Natural Community Types

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

The Three-horned moth is considered extremely rare and may be critically imperiled in Michigan. Little is known about this species' status, distribution, life history and ecology. As a result, little is known about specific threats to this species. Thus, specific management recommendations for this species can not be provided at this time. In general, surveys are needed to determine this species' current status and distribution in the state. Research to obtain information on this species' life history and ecology and assess threats to its conservation also is warranted. Industrial, residential or recreational development has likely threatened this species by causing significant habitat loss . The sites at which this species has been documented should be protected. Adequate and suitable habitat at these sites need to be maintained including sufficient densities of the species' host plant(s). The use of pesticides and herbicides, such as mosquito spraying, also may pose a significant threat to this species.

Active Period

Flight from third week of September to fourth week of October

Survey Methods

Larvae are present from May to July. Adults have been documented in Michigan from mid-September through October. The best way to survey for this species is by blacklighting at night during the adult flight period, a technique whereby a sheet is stretched across two trees or poles and an ultraviolet light is used to attract moths to the sheet. Moths can be collected directly from the sheet. Insects come to light usually in largest numbers on still, dark, cloudy nights when both temperature and humidity are high. Adults of this species also can be surveyed with bait traps (e.g., "sugaring" which consists of baiting moths by painting sugar syrup to trees). It is recommended that reports of this species be verified with a voucher specimen, photograph and/or verification by species expert.


Survey Period: From third week of September to fourth week of October

Time of Day: Evening
Humidity: Humid
Cloud Cover: Overcast
Air Temperature: Warm
Wind: No Wind
Survey Method Comment: Ideal survey conditions but surveys can be conducted under other conditions as well.

Time of Day: Night
Humidity: Humid
Cloud Cover: Overcast
Air Temperature: Warm
Wind: No Wind
Survey Method Comment: Ideal survey conditions but surveys can be conducted under other conditions as well.


Survey References

  • Covell, Charles. A Field Guide to the Moths of Eastern North America. Peterson Field Guide Series, Houghton Mifflin Company, Boston, MA. 496 pp.
  • Martin, J.E.H. 1977. The Insects and Arachnids of Canada (Part 1): Collecting, preparing, and preserving insects, mites, and spiders. Publication 1643. Biosystematics Research Institute, Ottawa.

Technical References

  • Forbes, W.T.M. 1954. Lepidoptera of New York and Neighboring States, Noctuidae, Part III. Cornell University Agricultural Experiment Station, NY. 433 pp.
  • Stehr, F. W. 1997. Michigan Lepidoptera Survey Sites and Seasonal Occurrence of Michigan's Listed Species Annual Report 1997. 30 pp.+ MI Lepidoptera Survey Data Collection Form