Moths of North Carolina
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152 NC Records

Isa textula (Herrich-Schäffer, 1854) - Crowned Slug Moth


Taxonomy
Superfamily: Zygaenoidea Family: LimacodidaeP3 Number: 660039.00 MONA Number: 4681.00
Comments: This is one of only two representatives of this genus in North America and the only one to occur in the East.
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: Wagner (2005)                                                                                 
Adult Markings: Isa textula lacks any conspicuous markings on the body or wings. The head, thorax, and abdomen vary from light reddish-tan or reddish-orange to reddish-brown and tend to be lighter colored that the forewings. The forewing varies from pale orange to dark reddish-brown and has subtle, textured bands of silvery gray scaling that gives it a unique, velvety appearance. The hindwing is concolorous with the forewing. The length from the tip of the head to the apex of the forewing at rest averages 10.5 mm (n = 8). This species has a conspicuous hump-backed shape when resting, with the head projecting downward towards the substrate.
Wingspan: 20 mm (Forbes, 1923)
Adult Structural Features: The male antenna is broadly pectinate to the apex, and the palps are truncate and only extend to the middle of the face. The hind tibia has only a single pair of spurs (Forbes, 1923).
Adult ID Requirements: Identifiable from good quality photos of unworn specimens.
Immatures and Development: Dyar (1896) studied the life cycle of I. textula in New York where the populations are single-brooded. The females lay their eggs singly on the undersides of leaves during July in New York. The first instar molts before feeding and the larvae feed on the undersides of leaves throughout the entire larval period. They pass through eight or nine instars, with the final instar ranging from 12.5-18.5 mm in length. After completing the feeding stage, the larva drops to the ground and spins a dense, dark brown, fibrous cocoon during September. Larvae in more southern populations typically remain active well into the autumn months and are often found feeding when the leaves are obtaining their fall colors. Larvae in North Carolina are commonly seen well into November and as late as early December. The larvae enter diapause shortly after spinning their cocoons, then pupate the following spring.

The late-instar larvae have highly flattened, oval, pale green bodies with conspicuous, finely tapering, greenish lobes around almost all of the perimeter of the body. The lobes bear numerous stinging spines that protrude outward from their perimeters. The anteriormost region has two horn-like structures and greatly reduced lobes, and is often edged with rusty brown coloration. The mid-dorsal region has two pale yellow longitudinal lines that run the entire length of the body, and the posterior half of the lines usually have two red spots that are bordered with yellow to yellowish white laterally (Dyar, 1896; Wagner, 2005). The larvae can deliver a mild to severe sting and cause dermatitis (Villas-Boas et al., 2016), so handle them with care.
Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants.
Distribution in North Carolina
Distribution: Isa textula occurs throughout most of the eastern US and in adjoining areas of Ontario and Quebec. In the US the range extends from Maine southward to southern Florida, and westward to central Texas, southeastern Oklahoma, Arkansas, Missouri, eastern Kansas, Illinois and Wisconsin. This species occurs statewide in North Carolina, from the barrier islands to the higher elevations in the Blue Ridge.
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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