Moths of North Carolina

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View PDF	Gracillariidae Members:	Macrosaccus Members:	52 NC Records

Macrosaccus robiniella (Clemens, 1859) - Black Locust Leafminer Moth

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Taxonomy

Superfamily:
Gracillarioidea

Family:
Gracillariidae

Subfamily:
Lithocolletinae

Tribe:
[Lithocolletini]

P3 Number:
33a0287

MONA Number:
790.00

Comments: Three Phyllonorycter species that occur in North Carolina were placed in a new genus, Macrosaccus, by Davis and De Prins (2011) based on differences in wing venation, genitalia, and life history traits. All are leafminers and have species-specific host plants.

Identification

Field Guide Descriptions: Beadle and Leckie, 2012 (as Phyllonorycter robiniella).

Online Resources: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLD

Technical Description, Adults: Davis and DePrins (2011)

Technical Description, Immature Stages: Davis and DePrins (2011)

Adult Markings: The following is based on detailed descriptions by Braun (1908) and Davis and De Prins (2011). The frons is smooth and shiny white, and the vertex is extremely rough. The vestiture consists of a tuft of elongate, piliform, mostly dark brown scales that are intermixed with white scales. The labial palps are white. The antenna is mostly dark fuscous dorsally for most of its length except the whitish tips, with the dark area narrowing to a more slender dark streak toward the basal 1/4–1/3 of its length. The thorax is dark brown dorsally, and the forewing pattern is complex. The ground color of the costal half is mostly light orange brown, while the basal third and dorsal half of the forewing are usually darker, mostly black to sometimes pale golden gray between the white streaks. There are four silvery costal streaks, the first two oblique. The first begins at about one-fourth the wing length. It is dark-margined on both sides and projects towards the middle of the first dorsal streak, which is dark margined on the anterior side. The second costal streak is at about the middle, is also dark margined on both sides, and nearly unites at an angle with an opposing first dorsal streak. The third costal streak at three-quarters nearly unites with the opposing second dorsal streak; both are dark-margined on the anterior side. A fourth white costal streak occurs just before the apex and is also dark margined on the anterior side. It projects towards the apex of the second dorsal streak. Between the first and second dorsal streaks there are one or two small black streaks. A black apical spot is present near the wing tip and the grayish fringe has a dark margin. The hindwing and fringe are uniformly gray. The legs are mostly dark fuscous dorsally with two or three dark annuli or bands on the tibia and tarsal region. Macrosaccus robiniella is morphologically similar to our other two Macrosaccus species. It has paired streaks at mid-wing rather than a complete fascia, as is typically the case with the other two species. As described at microleps.org, the basal part of the forewing of M. robiniella is solid gray, while in M. uhlerella and M. morrisella there is a small but distinct whitish patch near the dorsal margin at the outer limit of the basal gray area. In addition, M. morrisella also has a narrow white line that runs medially from the base of the forewing almost to the anterior edge of the white patch, thus creating a white marking that nearly encloses the basal gray area of the wing. Davis and De Prins (2011) noted that the forewing pattern of M. uhlerella is most similar to that of M. morrisella in having the basal strigulae less oblique than those present in M. robiniella. It differs from M. morrisella in lacking the distinct basal white streak typical of the latter. Braun (1908) noted that M. morrisella generally has a more shiny appearance than the other two species. All three species can be easily identified in the larval stages by their host plants and mine characteristics.

Wingspan: 6-6.5 mm (Braun, 1908)

Forewing Length: 2.3–3.1 mm (Davis and De Prins, 2011)

Adult Structural Features: Davis and De Prins (2011) provide detailed descriptions and illustrations of the male and female genitalia. The male genitalia are most similar to that of M. morrisella, in that the valva is only slightly constricted near apex (very strongly constricted near the middle in M. uhlerella). M. morrisella can be distinguished from M. robiniella by the fact that the valva is constricted before the apex, and the arms of transtilla are reduced. In M. robiniella the valva is constricted closer to apex and the arms of the transtilla are broader.

Adult ID Requirements: Identifiable from good quality photos of unworn specimens.

Immatures and Development: The larvae produce conspicuous silvery white blotch mines on the leaflets of Robinia spp. These are often oval-shaped, have smoothly rounded margins, and may have an initial linear portion that is often obliterated as the mine expands into a large blotch. The mines are initially flat, but become tentiform with time. They can be produced on either side of the leaflet (more commonly on the underside, but often on the upperside), and a single mine may contain more than one larva. Tissue damage causes the opposite leaf surface to develop fine whitish blotches that are intermixed with green tissue. These are most obvious on the upper surfaces of leaflets. Pupation occurs in a whitish silken cocoon within the mine (Davis and De Prins, 2011).

Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants.

Distribution in North Carolina

Distribution: Black Locust is native to the eastern US, but has been widely planted across much of the US, eastern Canada, Europe, and other regions of the world. Macrosaccus robiniella has expanded its range accordingly, and is now found in southern Canada (Ontario; New Brunswick), British Columbia, and throughout much of the northeastern and east-central states. Populations range as far south as North Carolina. As of 2021, our records are mostly from the Blue Ridge and Piedmont, with one record from the Sandhills. This species was introduced to Europe where it has become a pest on Black Locust. Records from British Columbia may also reflect possible introductions out west.

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
Immature 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: Local populations probably have two or more broods per year, with the first beginning after the spring leaf-out, and the final brood occurring in late summer or very early fall. As of 2021, our very limited records are from June in the Sandhills, and from August-September elsewhere.

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: Larvae feed primarily on Black Locust (Robinia pseudoacacia), but make occasionally use other species of Robinia, including Bristly Locust (R. hispida) and Clammy Locust (R. viscosa; Robinson et al. 2010, Eiseman 2019). In North Carolina, the majority of our records are from Black Locust, but Tracy Feldman has also recorded mines on Dwarf Locust (R. nana) and Bristly Locust in the Sandhills. - View

Observation Methods: Local populations are most easily documented by searching for the silvery white mines on Black Locust leaflets. Be sure to photograph both sides of the leaflet in order to eliminate species such as Odontota dorsalis (a beetle) that make full-depth mines. We encourage individuals to rear and photograph the adults whenever feasible.

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: The mines of this species are occasionally encountered along forested roadsides and open forests, but they far less abundant than those of the Locust Digitate Leafminer Moth (Parectopa robiniella).

Photo Gallery for Macrosaccus robiniella - Black Locust Leafminer Moth

65 photos are available. Only the most recent 30 are shown.

	Recorded by: Mark Basinger on 2025-10-01 Hoke Co. Comment:		Recorded by: Mark Basinger on 2025-10-01 Hoke Co. Comment:
	Recorded by: Jim Petranka, Marilyn Westphal and Becky Elkin on 2025-08-17 Henderson Co. Comment: Occupied mine was in a Black Locust leaflet.		Recorded by: Mark Basinger on 2025-08-15 Ashe Co. Comment:
	Recorded by: David George, Kevin Bischof, Rich Teper, Patrick Coin on 2025-08-15 Transylvania Co. Comment:		Recorded by: Mark Basinger on 2025-07-14 Richmond Co. Comment:
	Recorded by: Mark Basinger on 2025-07-14 Richmond Co. Comment:		Recorded by: Mark Basinger on 2025-07-14 Scotland Co. Comment:
	Recorded by: Mark Basinger on 2025-07-14 Scotland Co. Comment:		Recorded by: Jim Petranka, Mark Basinger and Becky Elkin on 2025-06-26 Mitchell Co. Comment:
	Recorded by: Mark Basinger, Jim Petranka, and Becky Elkin on 2025-06-26 Mitchell Co. Comment:		Recorded by: Mark Basinger on 2025-06-22 Buncombe Co. Comment:
	Recorded by: Mark Basinger on 2025-06-05 Wilson Co. Comment:		Recorded by: Jim Petranka on 2025-05-19 Cumberland Co. Comment: One of four specimens that were reared from Robinia nana. Mines collected on May 9; first adult on May 18.
	Recorded by: Jim Petranka, Becky Elkin, Tracy Feldman, David George, Jeff Niznik and John Petranka. on 2025-05-09 Cumberland Co. Comment:		Recorded by: Jim Petranka, Becky Elkin, Tracy Feldman, David George, Jeff Niznik and John Petranka. on 2025-05-09 Cumberland Co. Comment:
	Recorded by: Tracy Feldman, David George on 2025-05-09 Cumberland Co. Comment:		Recorded by: Tracy Feldman, David George on 2025-05-09 Cumberland Co. Comment:
	Recorded by: Tracy Feldman, David George on 2025-05-09 Cumberland Co. Comment:		Recorded by: Mark Basinger on 2024-09-21 Buncombe Co. Comment:
	Recorded by: Mark Basinger on 2024-09-06 Wilson Co. Comment:		Recorded by: Mark Basinger on 2024-09-02 Bladen Co. Comment:
	Recorded by: Mark Basinger on 2024-09-02 Bladen Co. Comment:		Recorded by: Jim Petranka on 2024-07-19 Madison Co. Comment:
	Recorded by: Ken Kneidel on 2023-10-14 Burke Co. Comment:		Recorded by: Ken Kneidel on 2023-10-14 Burke Co. Comment:
	Recorded by: Jim Petranka, Becky Elkin and Bo Sullivan on 2023-08-09 Ashe Co. Comment:		Recorded by: Jim Petranka, Becky Elkin and Bo Sullivan on 2023-08-08 Wilkes Co. Comment:
	Recorded by: David George, Stephen Dunn, Jeff Niznik on 2023-07-31 Macon Co. Comment:		Recorded by: David George, Stephen Dunn, Jeff Niznik on 2023-07-31 Swain Co. Comment: