Moths of North Carolina
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Isochaetes Members:
77 NC Records

Isochaetes beutenmuelleri (Hy. Edwards, 1887) - Spun Glass Slug Moth

Taxonomy
Superfamily: Zygaenoidea Family: LimacodidaeP3 Number: 660033.00 MONA Number: 4675.00
Comments: Isochaetes beutenmuelleri is the sole member of the genus in North America.
Identification
Field Guide Descriptions: Covell (1984); Beadle and Leckie (2012)Online Photographs: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLDTechnical Description, Adults: Forbes (1923)Technical Description, Immature Stages: Dyars (1907); Wagner (2005)                                                                                 
Adult Markings: This is one of the smaller limacodids with the length from the tip of the head to the apex of the forewing at rest averaging 8 mm (n = 8). The head, thorax, and forewing has a marbled patchwork of orange, dark brown, cream, rusty-red and black coloration, and the females tend to be darker than the males (Covell, 2005). There is a darker-edged, pale, oval mark that is centered in the subterminal area, but this mark is more difficult to discern on dark and worn individuals. The back of the head, thorax, and legs have prominent tufts of raised scales. The 'bottle brush" like middle pair of forelegs are particularly noticeable and are often held straight out from the body. The hindwings vary from reddish-brown to brown and approximate the overall color of the forewings.
Wingspan: 20 mm (Forbes, 1923)
Adult Structural Features: The male antennae are pectinate and the palps reach or exceed the vertex. The hind tibia has only a single pair of spurs in both sexes (Forbes, 1923).
Adult ID Requirements: Identifiable from good quality photos of unworn specimens.
Immatures and Development: Dyars (1907) studied this species in New York and noted that the females lay eggs singly on the undersides of leaves. The young instars skeletonize the undersides of leaves, leaving small patches of damaged tissue on the leaf, while the later instars consume the entire leaf.
Populations are univoltine in this area and pass through eight instars. The final instar moves to the ground where it spins a hard, round, dark-brown cocoon for overwintering. Pupation occurs in the spring, and the adult emerges after the spring leaf-out from a concealed lid on the cocoon.

The common name for this moth is derived from the delicate-looking caterpillar that has an oval, flattened body that is covered with fine hairs that resemble spun glass. The later instars are pale translucent green with 18 hairy arms that radiate from the perimeter of the body and taper to a point. The arms have fine, white, elongated hairs that criss-cross across the arms. The body is largely transparent, with the heart and gut visible and appearing as a dark green mid-dorsal stripe. The stripe is flanked by upright translucent knobs that have dozens of stinging spines (Dyars, 1907; Wagner, 2005). The number of elongated hairs on the eighth and final instar dramatically increases so that the body is scarcely visible. The last instar sheds the arms before spinning its cocoon.
Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants.
Distribution in North Carolina
Distribution: Isochaetes beutenmuelleri is mostly found in the southeastern US, with the range extending from Maryland and vicinity southward to central Florida, and westward to central Texas, eastern Oklahoma, Arkansas, southern Missouri, southern Illinois, southern Indiana, and southern Ohio. This species occurs in all three physiographic regions in North Carolina, but as of 2023 has not been documented at the higher elevations in the Blue Ridge, and appears to be rare in the southern two-thirds of the Coastal Plain.
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: The adults have been observed from March through October in different areas of the range, with the primary flight period from May through September. As of 2023, our records are from mid-May through late-August, with a seasonal peak in June and July. Populations in North Carolina are univoltine.
Habitats and Life History
Habitats: Most of our records come from wet to mesic stands of hardwoods, including bottomland and riparian forests, lakeshores, and mesic hardwoods.
Larval Host Plants: Dyars (1907) noted that the larvae are polyphagous and use a variety of hardwood species with smooth leaves, but did not specify which ones other than Northern Red Oak (Quercus rubra). Wagner (2005) and Heppner (2007) listed American Beech (Fagus grandifolia) and oaks as hosts. In North Carolina, we have recorded the species feeding on beech. - View
Observation Methods: The adults are attracted to lights, but may be better sampled using sheets rather than traps. Like other limacodids, it does not appear to come to bait or visit flowers.
Wikipedia
See also Habitat Account for General Hardwood Forests
Status in North Carolina
Natural Heritage Program Status:
Natural Heritage Program Ranks: G4 [S4]
State Protection: Has no legal protection, although permits are required to collect it in state parks and on other public lands.
Comments: Isochaetes beutenmuelleri occurs across a wide area of the state, although records are absent from or sparse in some areas, such as much of the southern Coastal Plain and the higher elevations in the mountains. This species is associated with fairly common habitats and host plants, and thus seems secure within the state.

 Photo Gallery for Isochaetes beutenmuelleri - Spun Glass Slug Moth

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

Recorded by: David George, Stephen Dunn, Jeff Niznik on 2023-08-18
Caswell Co.
Comment: 		Recorded by: David George, Stephen Dunn, Jeff Niznik on 2023-08-18
Caswell Co.
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Recorded by: David George, Stephen Dunn, Jeff Niznik, Rich Teper, Becky Watkins on 2023-07-30
Swain Co.
Comment: 		Recorded by: David George, Stephen Dunn, Jeff Niznik, Rich Teper, Becky Watkins on 2023-07-29
Swain Co.
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Recorded by: Jim Petranka on 2023-07-26
Madison Co.
Comment: 		Recorded by: Jim Petranka on 2023-07-21
Madison Co.
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Recorded by: David George, Jeff Niznik on 2023-07-19
Durham Co.
Comment: 		Recorded by: Simpson Eason on 2023-07-15
Durham Co.
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Recorded by: Jim Petranka on 2023-07-08
Madison Co.
Comment: 		Recorded by: John Petranka, David George on 2023-07-07
Orange Co.
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Recorded by: David George, Stephen Dunn, Jeff Niznik on 2023-07-06
Orange Co.
Comment: 		Recorded by: John Petranka on 2023-07-06
Orange Co.
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Recorded by: John Petranka on 2023-07-04
Orange Co.
Comment: 		Recorded by: John Petranka, David George on 2023-06-30
Orange Co.
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Recorded by: Dean Furbish on 2023-06-05
Wake Co.
Comment: 		Recorded by: Simpson Eason on 2022-08-31
Durham Co.
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Recorded by: David George, Lior Carlson, Brian Bockhahn on 2022-08-09
Rockingham Co.
Comment: 		Recorded by: Simpson Eason on 2022-07-31
Durham Co.
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Recorded by: Jim Petranka on 2022-07-15
Madison Co.
Comment: 		Recorded by: David George, L. M. Carlson, Stephen Dunn on 2022-07-15
Orange Co.
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Recorded by: Jim Petranka on 2022-07-13
Madison Co.
Comment: 		Recorded by: David George, L. M. Carlson on 2022-07-01
Chatham Co.
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Recorded by: John Petranka on 2022-06-29
Orange Co.
Comment: 		Recorded by: Ken Kneidel on 2022-06-26
Burke Co.
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Recorded by: Ken Kneidel on 2022-06-26
Burke Co.
Comment: 		Recorded by: David George, L. M. Carlson on 2022-06-21
Caswell Co.
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Recorded by: Dean Furbish on 2022-06-02
Wake Co.
Comment: 		Recorded by: Jeff Niznik on 2022-05-29
Chatham Co.
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Recorded by: Jeff Niznik on 2021-07-28
Wake Co.
Comment: 		Recorded by: Dean Furbish on 2021-07-22
Wake Co.
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