Thysanopyga intractata (Black-dotted Ruddy) Jim Vargo

Thysanopyga intractata (Black-dotted Ruddy)
Jim Vargo

Class
Insecta (Insects)
Family
Geometridae (Loopers, Span Worms, Inch Worms, Geometer Moths)
State Protection
Not Listed
Not listed or protected by New York State.
Federal Protection
Not Listed
State Conservation Status Rank
S1
Critically Imperiled in New York - Especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines.
Global Conservation Status Rank
GNR
Not Ranked - Global conservation status not yet assessed.

Summary

Did you know?

The grip of the caterpillar is strong making it difficult to remove from the foodplant (Wagner et al. 2001).

State Ranking Justification

Both Covell (1984) and Forbes (1948) consider this species rare in the north. There is one known occurrence in Suffolk County.

Short-term Trends

The short-term trends are unknown.

Long-term Trends

The long-term trends are unknown.

Conservation and Management

Threats

Specific threats to this species are unknown. Development and insecticide use are general threats. Also, 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

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).

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 gypsy 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 (Schweitzer et al. 2011).

Research Needs

Additional research is needed in New York to determine the number of broods and specific habitat needs.

Habitat

Habitat

The specific habitat is not known for black-dotted ruddy. There is one known extant occurrence in New York where it was found between either maritime dunes and maritime heathland or between sea level fen and maritime heathland. Larval foodplants are Hollies (Ilex spp.) (Wagner et al. 2001).

Associated Ecological Communities

  • 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. * probable association but not confirmed.
  • 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.

Range

New York State Distribution

There is one extant location for this species in Suffolk County.

Global Distribution

Black-dotted ruddy is found from Massachusetts south to Florida and Texas and west to Wisconsin.

Best Places to See

  • Napeague State Park (Suffolk County)

Identification Comments

Identifying Characteristics

This species has a wingspan of 2.1-3.1 cm. Covell (1984) describes the wings as deep orange to dull reddish- brown. There are three dark, indistinct lines. The postmedial line on the forewing is irregular with outwardly whitish dots. All wings have sharply-defined black discal dots (Covell 1984). The body color of the caterpillar ranges from green to brown. The green form can be somewhat translucent. It is free of warts or any other swellings. Mature larvae are under 2.5 cm (Wagner et al. 2001).

Best Life Stage for Proper Identification

Adult.

Diet

The larval foodplant is Holly (Ilex spp.). American holly may be the only host in the Northeast (Wagner et al. 2001).

Best Time to See

This species is most abundant as adults in July. Schweitzer (1998) states that they are present from March to December in New Jersey with peaks in July and October.

  • Present
  • Active

The time of year you would expect to find Black-dotted Ruddy present and active in New York.

Black-dotted Ruddy Images

Taxonomy

Black-dotted Ruddy
Ilexia intractata (Walker, [1863])

  • Kingdom Animalia
    • Phylum Mandibulata (Mandibulates)
      • Class Insecta (Insects)
        • Order Lepidoptera (Butterflies, Skippers, and Moths)
          • Family Geometridae (Loopers, Span Worms, Inch Worms, Geometer Moths)

Additional Resources

References

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

Forbes, William T. M. 1948. Lepidoptera of New York and neighboring states part II. Cornell University Agricultural Experiment Station Memoir 274.

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

New York Natural Heritage Program. 2019. 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.

Schweitzer, Dale F. 1998. Rare, potentially rare, and historic macrolepidoptera for Long Island, New York: A suggested inventory list.

Wagner, D.L., D.C. Ferguson, T.L. McCabe, and R.C. Reardon. 2001. Geometrid caterpillars of northeastern and Appalachian forests. USDA, Forest Service, Forest Health Technology Enterprise Team, FHTET-2001-10, Washington, DC. 239 pp.

Links

About This Guide

Information for this guide was last updated on: June 27, 2012

Please cite this page as:
New York Natural Heritage Program. 2019. Online Conservation Guide for Ilexia intractata. Available from: https://guides.nynhp.org/black-dotted-ruddy/. Accessed May 20, 2019.

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