Moths of North Carolina
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15 NC Records

Agonopterix robiniella (Packard, 1869) - Four-dotted Agonopterix Moth


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Taxonomy
Superfamily: Gelechioidea Family: DepressariidaeSubfamily: DepressariinaeTribe: [Depressariini]P3 Number: 420095.00 MONA Number: 882.00
Comments: Agonopterix is a large holarctic genus with more than 125 species, with most occurring in the Palearctic Region. Currently, there are 47 recognized species in North America. Our species are largely confined to the western mountains.
Identification
Field Guide Descriptions: Covell (1984); Beadle and Leckie (2012)the US Online Photographs: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLDTechnical Description, Adults: Clarke (1941); Hodges (1974)Technical Description, Immature Stages: Packard (1869)                                                                                 
Adult Markings: The following is based on descriptions by Clarke (1941) and Hodges (1974). The labial palp is whitish ochreous basally, and gradually becoming more yellowish toward the apex. The second segment is mottled with brick red and fuscous exteriorly. The third segment has two annuli; a sub-basal annulus that is brick-red, and a subterminal annulus that is more fuscous than the sub-basal annulus. The antenna is fuscous with considerable red scaling basally. The head, thorax, and ground color of the forewing is yellow, mottled and overlaid with brick red, and shaded with fuscous and black. Small black flecks are scattered throughout. At the basal third of the forewing there are two black discal spots. The one nearer the inner margin is less distinct than the one towards the costa and is sometimes not readily evident. The discal spot at the end of cell is either absent or very indistinct. The dark patterning on the wing is variable, but most specimens have a dark, diffuse curved band that extends from slightly beyond the middle of the costa to the inner margin near the wing base. A lateral branch is usually present that extends posteriorly from near the cell towards the inner margin. Before the termen, there is a poorly defined dark band or blotch that does not reach the costa. A series of indistinct blackish spots occurs along the costa and around the termen. The cilia is light fuscous and tinged with red. The hindwing is grayish fuscous with the terminal edge narrowly blackish fuscous. The cilia is light fuscous with narrow sub-basal and sub-terminal bands. The legs are whitish ochreous and suffused and mottled with brick red and fuscous.

This species is similar to A. thelmae, which has a red to reddish-orange streak along the cell (almost always absent in A. robiniella) and a small dark blotch adjoining it on the costal side. Agonopterix thelmae also lacks a brick-red sub-basal annulus on the third segment of the labial palp (present in A. robiniella) and has two dark anterior discal spots that are oblique. In many cases the inner spot is greatly reduced in A. robiniella, giving the appearance of a single spot. Agonopterix dimorphella also superficially resembles A. robiniella, but is darker and smaller, and has a pale yellow spot at the end of the cell.
Wingspan: 14-20 mm (Clarke, 1941).
Forewing Length: 6.9-11.0 mm (Hodges, 1974)
Adult Structural Features: Clarke (1941) provides detailed descriptions and illustrations of the male and female genitalia, and Hodges (1974) discusses genitalic differences that are useful in distinguishing A. robiniella from A. thelmae. In particular, males of A. robiniella have the transtilla slightly indented medially, whereas it is uniformly broad in A. thelmae. In A. robiniella the heavily sclerotized costal margin of the sacculus usually is equal to the length of the process, whereas in A. thelmae it is 1/4 to 1/3 longer than the process. In the female the anterior margin of the eight abdominal sternum is straight in A. robiniella, while in A. thelmae it bears a rounded medial projection.
Structural photos
Adult ID Requirements: Identifiable from good quality photos of unworn specimens.
Immatures and Development: Packard (1869) described the larvae that were feeding on 'locust' (presumably Black Locust) during the last week of June. The larvae were greenish, with a black head and green cervical shield. They drew the leaflets together with silk threads and in some cases nearly defoliated individual branches. The larvae also consumed the flower buds.
Distribution in North Carolina
Distribution: Agonopterix robiniella is found in eastern North America in southern Canada (Ontario; Quebec; Nova Scotia; New Brunswick), and from the northeastern states westward and southwestward to Minnesota, Oklahoma, Arkansas, Alabama, and western North Carolina. This species is absent from most of the southeastern Piedmont and Coastal Plain, and appears to have expanded its range substantially since European colonization due to the planting and escape of Black Locust outside of its native range. As of 2020, all of our records except one are from the lower elevations in the mountains.
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)

Click on graph to enlarge
Flight Comments: This species is univoltine, with breeding occurring after Black Locust is leafed-out. Adults have been found from April through October in different areas of the range, with peak in June-Aug. As of 2020, our records extend from June through August.
Habitats and Life History
Habitats: Local populations are strongly dependent on Black Locust for successful reproduction. This species is common in edge habitats such as along roadways or fencerows, but also occurs in mesic hardwood forests in the mountains, particularly where past disturbance has allowed seedlings to become established.
Larval Host Plants: The larvae rely heavily on Black Locust (Robinia pseudoacacia), but will occasionally use Honey Locust (Gleditsia triacanthos) and possibly other species of Robinia (Schaffner, 1959; Prentice, 1966; Ferguson, 1975; Robinson et al., 2010). Isolated reports of this species using an oak (Covell, 1984) and snakeroot (Sanicula; Robinson et al., 2010) are questionable and need to be verified with additional observations. - View
Observation Methods: The adults are attracted to lights. Additional information is needed on the larval ecology, so we encourage naturalists to search for the larvae on Black Locust and document the life cycle.
Wikipedia
See also Habitat Account for Locust Groves and Thickets
Status in North Carolina
Natural Heritage Program Status:
Natural Heritage Program Ranks: GNR SU
State Protection: Has no legal protection, although permits are required to collect it on state parks and other public lands.
Comments: We have only a few records for this species as of 2020, which suggests that it may be uncommon in the state. Additional information on its distribution and abundance is needed before we can accurately assess its conservation status.

 Photo Gallery for Agonopterix robiniella - Four-dotted Agonopterix Moth

Photos: 6

Recorded by: David George, Stephen Dunn, Jeff Niznik, Rich Teper, Becky Watkins on 2023-07-30
Swain Co.
Comment: 		Recorded by: Jim Petranka and Becky Elkin on 2022-08-14
Madison Co.
Comment:
Recorded by: Kyle Kittelberger, Brian Bockhahn on 2020-07-15
Polk Co.
Comment: 		Recorded by: Vin Stanton on 2019-08-16
Buncombe Co.
Comment:
Recorded by: Vin Stanton on 2013-06-26
Buncombe Co.
Comment: 		Recorded by: Bo Sullivan on 0000-00-00
Ashe Co.
Comment: A comparison of A. thelmae (upper row) with A. robiniella (lower row).