Northern Oak Hairstreak

Satyrium favonius ontario (W. H. Edwards, 1868)

Oak Hairstreak
Erik Nielson

Insecta (Insects)
Lycaenidae (Blues, Coppers, Hairstreaks, Elfins)
State Protection
Not Listed
Not listed or protected by New York State.
Federal Protection
Not Listed
State Conservation Status Rank
Imperiled or Vulnerable in New York, or Apparently secure - Conservation status is uncertain; could be very vulnerable, or vulnerable, to disappearing from New York due to rarity or other factors, or could be uncommon but not rare in New York. More information is needed to assign either S2, S3 or S4.
Global Conservation Status Rank
Apparently Secure globally - The subspecies/variety is uncommon in the world but not rare; usually widespread, but may be rare in some parts of its range; possibly some cause for long-term concern due to declines or other factors. (The species as a whole is common globally.)


Did you know?

The Northern Oak Hairstreak is thought to be a canopy dwelling species (Gagliardi et al. 2017).

State Ranking Justification

According to a study done by Gagliardi et al. (2017), many parts of southeastern New York contain habitat suitable for the Northern Oak Hairstreak. However, habitat in this region of the state is fragmented and reduced by development. This species is believed to be a canopy dweller (Gagliardi et al. 2017), therefore, it is possible it is more common than indicated by ground surveys (Gagliardi et al. 2017). This species could be more widespread in parts on Long Island.

Conservation and Management


The main threat to this species is habitat loss. Control for Spongy Moth (Lymantria dispar) with chemical biocides, such as Dimilin, could severely threaten populations. Dimilin has been known to persist within the environment and on foliage for months (Schweitzer et al. 2018). In addition, Bt (Bacillus thuringiensis - a bacterial biological control used on Spongy Moth larvae) may have the potential to be lethal to Northern Oak Hairstreak larvae but additional studies are needed. In comparison, it is likely that Bt mortality would be lower than from Dimilin. Competition between Spongy Moth and Northern Oak Hairstreak larvae should not be a concern as normally Northern Oak Hairstreak larvae feed well before defoliation of oaks by Spongy Moth larvae.

Conservation Strategies and Management Practices

In most cases, the protection and preservation of habitat should be the main focus of preserving this species. Managers should consider ensuring that nectar species are present. Implement a cutting or mowing schedule that maintains or increases available native nectar sources, such as milkweeds and dogbanes, when they are in flower. Additionally, the use of Bt and Dimilin should be closely monitored to prevent accidental mortality of rare or threatened Lepidoptera.

Research Needs

More research is needed to identify which species of oaks the larvae eat and whether they have any other special needs. It would also be very useful to document the sensitivity of the larvae to realistic doses of Bt such as are applied for Spongy Moth suppression. The available evidence for other butterflies in the subfamily Theclinae suggests that this species would be sensitive to Bt (Schweitzer 2004; Wagner et al. 1996), but sensitivity of caterpillars to Bt is variable, even among species in the same genus (Peacock et al. 1998).



This species is typically found within oak forests or along their edge (Conserve Wildlife Foundation of New Jersey 2021). In some cases, it may be found where pitch pine and scrub oak may be present, but this butterfly is not generally found in classic pine barrens habitats. It may also turn up around more mixed forests.

Associated Ecological Communities

  • Appalachian oak-hickory forest* (guide)
    A hardwood forest that occurs on well-drained sites, usually on ridgetops, upper slopes, or south- and west-facing slopes. The soils are usually loams or sandy loams. This is a broadly defined forest community with several regional and edaphic variants. The dominant trees include red oak, white oak, and/or black oak. Mixed with the oaks, usually at lower densities, are pignut, shagbark, and/or sweet pignut hickory.
  • Coastal oak-hickory forest* (guide)
    A hardwood forest with oaks and hickories codominant that occurs in dry, well-drained, loamy sand of knolls, upper slopes, or south-facing slopes of glacial moraines of the Atlantic Coastal Plain.
  • Pitch pine-oak forest* (guide)
    A mixed forest that typically occurs on well-drained, sandy soils of glacial outwash plains or moraines; it also occurs on thin, rocky soils of ridgetops. The dominant trees are pitch pine mixed with one or more of the following oaks: scarlet oak, white oak, red oak, or black oak.

* probable association but not confirmed.


New York State Distribution

This species is mostly found in the lower Hudson Valley and on Long Island in New York State. The distribution also includes the Albany Pine Bush where one was collected in 1979. Historically, it was present in at least the Ithaca area, but according to Robert Dirig there have not been reports in the area since 1970, after collections in 1890, 1967, and 1970. Since 2000, there have been credible reports from Orange, Westchester, Rockland, and Suffolk counties. As Shapiro (1974) noted, the habitat is not rare in southeastern New York.

Global Distribution

The original specimen supposedly came from Ontario, Canada. However, since 1900 this subspecies has been found from the vicinity of Boston, Massachusetts (not before about 1980) south though coastal New England, southeastern New York, and then more widely from New Jersey through most of Georgia and west into Texas and Oklahoma. While it does occur in much of the lower Midwest east into Ohio and widely in the southeastern states, this species is unknown from the mountains.

Identification Comments

Identifying Characteristics

This species has a wingspan of 2.2-3.8 cm and can be characterized by its single tail at the base of each hindwing. The underside of both the forewing and hindwing are gray-brown in color. Postmedian bands are black and white; on the hindwings, the bands form a “M” (or "W") shape (Conserve Wildlife Foundation of New Jersey 2021). Advancing from the tail on the underside of the wings are a blue tail-spot with orange radiating from the top and bottom (Conserve Wildlife Foundation of New Jersey 2021). Larvae are a pale green color with yellow and green lateral striping (Conserve Wildlife Foundation of New Jersey 2021).

Characters Most Useful for Identification

Note the inwardly pointed "v" mark next to the largest white spot on the hindwing beneath and the prominent "M" (or "W") formed by the inner most line. These two markings together should be diagnostic. There is never any blue above. Live individuals always land with the wings closed. The flight season is also a clue to species, as this species will only be seen in or near New York in June and about the first half of July.

Best Life Stage for Proper Identification

This should be identified as an adult, but an expert on hairstreaks might be able to identify the larva. See Allen et al. (2005).


The Northern Oak Hairstreak is thought to be a canopy dwelling species (Gagliardi et al. 2017), though adults can commonly be found feeding on flower nectar in the late afternoon (Opler and Krizek 1984).


Larvae are known to feed on various oak (Quercus spp.) species (NatureServe 2021). Adults are found feeding on nectar from various flowering plants such as dogbane (Apocynum cannabinum), New Jersey tea (Ceanothus americanus), common milkweed (Asclepias syriaca), and white sweet clover (Melilotus albus) (Opler and Krizek 1984).

Best Time to See

The adults occur for less than a month in any given year, from about mid-June into mid-July. They often start a few days earlier than the other single-brooded early summer hairstreaks, but commonly occur with the others. The eggs overwinter on oaks and the larvae feed on the new growth in spring, probably finishing about the first of June in most years. There is only one brood in all parts of the range of this species. The adults visit flowers most often late in the day, usually after 16:00 hours.

  • Present
  • Reproducing
  • Larvae present and active
  • Eggs present outside adult

The time of year you would expect to find Northern Oak Hairstreak present, reproducing, larvae present and active, and eggs present outside adult in New York.

Similar Species

  • White-m Hairstreak (Parrhasius m-album) (guide)
    White-m Hairstreak is grayer than the Northern Oak Hairstreak. There is a small white dot on the leading edge of the hindwing of the White-m Hairstreak and the orange spot is larger and touches the "M" shape.
  • Oak Hairstreak (Satyrium favonius)
    The two species look very similar other than the Southern Oak Hairstreak is considered brighter than the Northern Oak Hairstreak.
  • Gray Hairstreak (Strymon melinus)
    Gray Hairstreak is grayer than Northern Oak Hairstreak and it has orange on its postmedian bands. This species prefers open to lightly wooded habitats and the foodplants are herbaceous.

Northern Oak Hairstreak Images


Northern Oak Hairstreak
Satyrium favonius ontario (W. H. Edwards, 1868)

  • Kingdom Animalia
    • Phylum Arthropoda (Mandibulates)
      • Class Insecta (Insects)
        • Order Lepidoptera (Butterflies, Skippers, and Moths)
          • Family Lycaenidae (Blues, Coppers, Hairstreaks, Elfins)


  • Fixsenia favonius ontario

Comments on the Classification

This species is usually placed in the genus Satyrium, currently. Older works considered northern populations (subspecies ontario) as a separate species.

Additional Resources


Allen, T.J., J.P. Brock, and J. Glassberg. 2005. Caterpillars in the field and garden. Oxford University Press, New York. 232 pp.

Brock, J. P., and K. Kaufman. 2003. Butterflies of North America. Kaufman Focus Field Guides, Houghton Mifflin Company, New York, NY 284 pp.

Conserve Wildlife Foundation of New Jersey. 2021. [web application]. Conserve Wildlife Foundation of New Jersey, Princeton, New Jersey. Available (Accessed: July 16, 2021).

Gagliardi, Benedict L., D. L. Wagner, J. M. Allen. 2017. Species distribution model for the ‘northern’ oak hairstreak (Satyrium favonius ontario) with comments on its conservation status in the northeastern united states. J Insect Conserve 21:781-790.

Glassberg, J. 1993. Butterflies through binoculars: A field guide to butterflies in the Boston-New York-Washington region. Oxford University Press: New York. 160 pp.

Glassberg, J. 1999. Butterflies Through Binoculars: The East. Oxford University Press, New York, New York. 400 pp.

Gochfeld, M. and J. Burger. 1997. Butterflies of New Jersey. Rutgers University Press: Rutgers, New Jersey. 327 pp.

Iftner, D. C., J. A. Shuey, and J. V. Calhoun. 1992. Butterflies and Skippers of Ohio. Ohio Biological Survey Bulletin. New Series, Vol. 9, no. 1, xii + 212 pp., 40 color plates.

Lotts, Kelly and Thomas Naberhaus, coordinators. 2022. Butterflies and Moths of North America for Satyrium favonius ontario. Dataset accessed 2022-02-08 at

NatureServe. 2021. NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available (Accessed: July 12, 2021).

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

O'Donnell, J.E., L.F. Gall., and D.L. Wagner, eds. 2007. The Connecticut Butterfly Atlas. State Geological and Natural History Survey of Connecticut, Department of Environmental Protection, Hartford. 376 pp.

Opler, P. A., and A. D. Warren. 2002. Butterflies of North America. 2. Scientific Names List for Butterfly Species of North America, north of Mexico. C.P. Gillette Museum of Arthropod Diversity, Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado. 79 pp.

Opler, Paul A. and G. Krizek. 1984. Butterflies East of the Great Plains. The Johns Hopkins University Press, Baltimore.

Peacock, J. W., D. F. Schweitzer, J. L. Carter, and N. R. Dubois. 1998. Laboratory Assessment of the effects of Bacillus thuringiensis on native Lepidoptera. Environmental Entomology 27(2):450-457.

Schweitzer, Dale F. 2004. Gypsy Moth (Lymantria dispar): impacts and options for biodiversity-oriented land managers. NatureServe, Arlington, Virginia. NatureServe Explorer. Online. Available:

Schweitzer, Dale F., M. C. Minno, and D. L. Wagner. 2018. Rare, declining, and poorly known butterflies and moths (lepidoptera) of forests and woodlands in the eastern united states. U.S. Forest Service.

Shapiro, A.M. 1974. Butterflies and Skippers of New York State. Search 4:1-60.

Wagner, D.L., J.W. Peacock, J.L. Carter, and S.E. Talley. 1996. Field assessment of Bacillus thuringiensis on nontarget Lepidoptera. Environmental Entomology 25(6):1444-1454.


About This Guide

This guide was authored by: Every, Zane W.

Information for this guide was last updated on: June 30, 2022

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Satyrium favonius ontario. Available from: Accessed June 23, 2024.