Moths of North Carolina
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View PDFGeometridae Members: 1 NC Records

Hydriomena exculpata Barnes & McDunnough, 1917 - No Common Name


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Taxonomy
Superfamily: Geometroidea Family: GeometridaeSubfamily: LarentiinaeTribe: HydriomeniniP3 Number: 910061.00 MONA Number: 7223.00
Comments: One of 56 species in this genus that occur in North America north of Mexico (McDunnough, 1954, covered 55 and Rindge added Hydriomena peratica in 1956). Most are boreal or are found in the West, with only five recorded in North Carolina.
Species Status: McDunnough placed exculpata in his Group I, which also includes the other four species found in our state. Of the three subspecies of exculpata recognized by McDunnough, only nanata occurs in the east, described by McDunnough from specimens from the White Mountains of New Hampshire and Canada. However, the one specimen from North Carolina does not resemble nanata but instead looks more like the nominate subspecies found in the Pacific Northwest (Ferguson, 1997).
Identification
Field Guide Descriptions: Online Photographs: MPG, BugGuide, iNaturalist, Google, BAMONATechnical Description, Adults: McDunnough (1954)                                                                                 
Adult Markings: A small, pale-brown Carpet. The basal and postmedial (between the median and postmedian lines) on the forewing are grayish-white with a slight brown shade; the antemedial and subterminal, and terminal areas are brown with a reddish shade. The antemedian, median, and postmedian lines are all black and well-defined. The antemedian is particularly strongly marked as is a strong black line runs adjacent to the inner margin, connecting the antemedian and median lines. A short black apical dash is also present, followed below by two subterminal black dashes. Hindwings are buff-colored.
Wingspan: 33 mm (measured from an illustration on the CFIB website)
Adult Structural Features: McDunnough (1954) describes the uncus of nominate subspecies as having a strongly swollen neck, whereas that of subspecies josepha and nanata as having a long, thin neck and possessing prominent basal tubercles. Although Ferguson (1997) noted that the North Carolina specimen more strongly resembled the nominate subspecies than ssp. nanata, he did not indicate whether that was true for just the wing markings or whether it also applied to the genitalia.
Adult ID Requirements: Identifiable from good quality photos of unworn specimens.
Immatures and Development: A description of the larvae and other early stages was not found
Distribution in North Carolina
Distribution: Known in North Carolina solely from Mt. Mitchell
County Map: Clicking on a county returns the records for the species in that county.
Flight Dates:
 High Mountains (HM) ≥ 4,000 ft.
 Low Mountains (LM) < 4,000 ft.
 Piedmont (Pd)
 Coastal Plain (CP)

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Flight Comments: Unrecorded but adults probably fly in mid-summer
Habitats and Life History
Habitats: Presumably Spruce-Fir Forest or Northern Hardwoods
Larval Host Plants: Information not found
Observation Methods: Not recorded
Wikipedia
See also Habitat Account for Spruce-Fir Forests
Status in North Carolina
Natural Heritage Program Status: SR
Natural Heritage Program Ranks: GU SH
State Protection: Listed as Significantly Rare by the Natural Heritage Program. That designation, however, does not confer any legal protection, although permits are required to collect it on state parks and other public lands.
Comments: Like several other species restricted to the summits of our highest mountains, this species appears to be a Pleistocene relict, associated with the spruce-fir forests and northern hardwoods typically found much farther north. The next nearest extant populations, in fact, appear to be those in the White Mountains of New Hampshire, although it is not clear whether our population belongs to subspecies nanata found in that area or the nominate form found in the Pacific Northwest. In any case, exculpata appears to be at extreme risk due both to global climate change and to the destruction of the remnant Spruce-Fir Forest ecosystems in our mountains. Whether or not it still exists in the state is currently unknown, but it is undoubtedly one of our rarest species and of significant conservation concern.