Imperial Moth

Eacles imperialis imperialis (Drury, 1773)

Eacles imperialis (Imperial Moth)
Jim Vargo

Insecta (Insects)
Saturniidae (Giant Silkworm and Royal Moths)
State Protection
Not Listed
Not listed or protected by New York State.
Federal Protection
Not Listed
State Conservation Status Rank
Unrankable - Currently unrankable due to lack of information or due to substantially conflicting information about status or trends.
Global Conservation Status Rank
Secure globally - Both the species as a whole and the subspecies/variety are common in the world; widespread and abundant (but may be rare in some parts of its range).


Did you know?

There are two Imperial Moth subspecies: Eacles imperialis pini and Eacles imperialis imperialis. The pini subspecies feeds exclusively on pines, while the imperialis subspecies feeds on several different tree species.

State Ranking Justification

Additional surveys are needed before assigning a state rank. As of 2012, there are five extant occurrences in New York State. Occurrences are known to be in the northern portion of the state and on Long Island, but not in between.

Short-term Trends

The short-term trends are unknown.

Long-term Trends

Populations declined in the mid-twentieth century most likely because of increased use of pesticides, metal halide bulbs, and the introduction of parasitoids, such as Compsilura concinnata (tachinid fly) that was introduced in 1906 (Goldstein 2010; Hedbor 2006, Schweitzer et al. 2006).

Conservation and Management


This species is believed to be severely impacted by pesticides and parasitoids, such as Compsilura concinnata tachinid fly (Goldstein 2010; Hedbor 2006).

This species is attracted to artificial lighting. Artificial lighting can: increase predation risk, disrupt behaviors such as feeding, flight, and reproduction, and interfere with dispersal between habitat patches. In addition, many individuals die near the light source. It is not known if the impact of artificial lighting is severe, but the impact is likely greater for small, isolated populations (Schweitzer et al. 2011).

Conservation Strategies and Management Practices

Insecticide use should be avoided when possible if rare species are present. When insecticide use cannot be avoided, careful planning along with consistent rare species monitoring, can result in successful eradication of the target species without eliminating rare species. A biocontrol alternative is Bacillus thuringiensis (Btk) for some target species, such as spongy moths. However, sensitivity to Btk varies among native species and this option should be fully researched for treatment timing and regimes and weighed with other options to have the least impact on native lepidopteran populations. Spongy moth management should be well planned to minimize impacts to rare species when they are present. However, spongy moths can also cause severe forest defoliation. This can lead to the starvation of larvae. The greatest impact is when defoliation occurs in consecutive years. Often, summer-feeding lepidopterans can be the most affected because they often need to feed on mature oak leaves. When they are forced to only eat the regrowth (young leaves), they tend to be undersized compared to larvae that are feeding on mature leaves (Schwietzer et al. 2011). There are two other spongy moth biocontrols that are currently unavailable, but appear to be very effective at eliminating spongy moths with little effect on non-target species: Gypchek (a viral preparation) and Entomophaga maimaiga (a fungus).

Minimizing lighting to maintain dark sky conditions would be beneficial. When lighting is necessary, it's best to use lights that emit red or yellow light because insects are generally not attracted to those colors. However, many sodium lights, which emit yellow light, are so bright that they do attract some insects. The best lighting appears to be low pressure sodium lights which have little effect on flying insects (Schweitzer et al. 2011).

Research Needs

Additional research is needed to gain a better understanding of this species' life history and habitat needs.



In the northern portion of its range, this species has been found in calcareous pavement barrens. On Long Island, the precise habitat has not been verified, except that captures were made between maritime grassland and maritime dunes or between a sea level fen and maritime heathland. The following trees have been recorded as foodplants: basswood, birches, cedar, elms, maples, oaks, pines, and walnut.

Associated Ecological Communities

  • Calcareous pavement woodland (guide)
    An open canopy woodland that occurs on very shallow soils over flat, striated outcrops of calcareous bedrock (limestone and dolomite).
  • Maritime dunes* (guide)
    A community dominated by grasses and low shrubs that occurs on active and stabilized dunes along the Atlantic coast. The composition and structure of the vegetation is variable depending on stability of the dunes, amounts of sand deposition and erosion, and distance from the ocean.
  • Maritime grassland* (guide)
    A grassland community that occurs on rolling outwash plains of the glaciated portion of the Atlantic coastal plain, near the ocean and within the influence of offshore winds and salt spray.
  • Maritime heathland* (guide)
    A dwarf shrubland community that occurs on rolling outwash plains and moraine of the glaciated portion of the Atlantic coastal plain, near the ocean and within the influence of onshore winds and salt spray.

* probable association but not confirmed.


New York State Distribution

Imperial moths have been found in the following counties in New York: Suffolk, Jefferson, and Seneca.

Global Distribution

Imperial moths can be found from southern Quebec and Maine south to Florida and west to western Ontario, Kansas, and Texas.

Best Places to See

  • Chaumont Barrens Preserve (Jefferson County)
  • Hither Hills State Park (Suffolk County)

Identification Comments

Identifying Characteristics

Imperial moth is a large moth with a wingspan between 8 and 17.4 cm. It has yellow wings with spotting and shading variations of pink, orange, or purplish brown. Males tend to be more heavily marked than females, especially to the south (Covell 1984). A full grown larva is 75 to 100 mm long. There are two color variations: green and brown. The body has long whitish hairs. The second and third thoracic segments each have two stubby, rough "horns" and a rows of smaller spines along the rest of the body. There are large black and yellow plates on the last abdominal segment. Oval, yellow to cream spiracles are found on the sides. The brown variation has tan to reddish brown horns and spines. The pupa are large, spinose, and very active when handled (Tuskes et al. 1996). Large, yellow eggs are laid on either side of the foodplant singly or in small groups (Hyche 2000, Tuskes et al. 1996).

Best Life Stage for Proper Identification



Adult males are very strong fliers. This species pupates underground in loose soil. It is very active when handled (Tuskes et al. 1996).


Larval foodplants are many tree species including: basswood, birches, cedar, elms, maples, oaks, pines, and walnut.

Best Time to See

Imperial moths can be found May through July in the northern portion of its range. There is one brood each year (Covell 1984).

  • Present
  • Active

The time of year you would expect to find Imperial Moth present and active in New York.

Similar Species

  • Imperial Moth (Eacles imperialis pini)
    The pini subspecies is smaller with more pink and has a strong postmedial line on the hindwing.

Imperial Moth Images


Imperial Moth
Eacles imperialis imperialis (Drury, 1773)

  • Kingdom Animalia
    • Phylum Arthropoda (Mandibulates)
      • Class Insecta (Insects)
        • Order Lepidoptera (Butterflies, Skippers, and Moths)
          • Family Saturniidae (Giant Silkworm and Royal Moths)

Additional Resources


Beadle, D. and S. Leckie. Peterson field guide to moths of Northeastern North America. Houghton Mifflin Harcourt: New York, NY.

Covell, Charles V. 1984. A field guide to the moths of eastern North America. Houghton Mifflin Company, Boston.

Goldstein, Paul Z. 2010. Life history of the Imperial Moth Eacles imperialis (Drury) (Saturniidae: Ceratocampinae) in New England, U.S.A.: distribution, decline, and nutritional ecology of the relictual islandic population. Journal of Research o the Lepidoptera 42 2003: 34-49.

Hedbor, James. 2006. Eacles imperialis (Imperial Moth) gaining ground in Vermont? Vermont Entomological Society News 52 (summer 2006): 4.

Hyche, L.L. 2000. Imperial Moth Eacles imperialis (Drury) (Saturnidae). Department of Entomology and Plant Pathology, Auburn University.

NatureServe. 2011. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available (Accessed: April 17, 2012 ).

New York Natural Heritage Program. 2024. New York Natural Heritage Program Databases. Albany, NY.

Schweitzer, D.F., M.C. Minno, and D.L. Wagner. 2011. Rare, Declining, and Poorly Known Butterflies and Moths (Lepidoptera) of Forests and Woodlands in the Eastern United States. USFS Technology Transter Bulletin, FHTET-2009-02.

Tuskes, P. M., J. P. Tuttle, and M. M. Collins. 1996. The Wild Silk Moths of North America: A Natural History of the Saturniidae of the United States and Canada. Cornell University Press, Ithaca, New York. 250 pp.


About This Guide

Information for this guide was last updated on: June 28, 2012

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Eacles imperialis imperialis. Available from: Accessed May 26, 2024.