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Field Guide Descriptions: | Online Photographs: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLD | Technical Description, Adults: Heppner (2023) | Technical Description, Immature Stages: Kearfott (1902) | |
Adult Markings: The following description is based on that of Heppner (2023). The head and palps are grayish-brown with white-tipped scales, while the antennae are white with blackish-brown annulations. The thorax is grayish-brown with white-tipped scales, and often with a small orange band on each side. The forewing ground is dark brown with white-tipped scales at one-third and distally that form diffuse vertical or oblique frosted bands. The wing base has a longitudinal orange streak on the costal half, while the dorsal half is dark brown with scales that are sometimes white-tipped. The costa has a patch of dull orange and dark brown near the middle, with heavily frosted bands on either side. Large blackish blotches that have silvery metallic iridescent marks are present on the distal third of the wing. The fringe along the termen is pale white with a dark grayish-brown line in the middle. The hindwing is pale brown with a diffuse white submarginal crescent near the tornus. The fringe is white with two broad brown lines.
The adults closely resemble Tebenna gnaphaliella and are best distinguished by the single orange streak at the forewing base versus two bars in T. gnaphaliella. These species also differ in wingspan, with T. gnaphaliella being smaller (7.4-10 mm) than Pseudotebenna carduiella (11.5-14 mm).
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| Wingspan: 11.5-14 mm (Heppner, 2023) |
| Adult Structural Features: Heppner (2023) has illustrations and descriptions of the male and female genitalia. He notes that the primary ways to distinguish members of the newly created genus Pseudotebenna from Tebenna are, 1) the simplified male genitalia with short valvae that are merely notched apically distal to a single hook-like appendage directed ventrally (valval apex with distal thorn-like projection and divided ventral setose lobes in Tebenna), 2) an extended saccus (short in Tebenna) and 3) an aedeagus that lacks a caulis and has a twisted cornutus in addition to a long flechette cornutus (caulis present and lacking any twisted extra cornutus in Tebenna). In females the sterigma has a caudal projection (lacking in Tebenna), the ductus bursae is offset before the extension to the bursa (mostly continuous in Tebenna), and the signum is diffuse or a curved keel versus prominently keel-like in Tebenna. |
| Adult ID Requirements: Identifiable from good quality photos of unworn specimens. |
| Immatures and Development: The larvae are specialist on thistles (Cirsium). Kearfott (1902) studied larvae that were feeding on C. spinosissimiis in New Jersey. The larvae are stem borers and feed communally in thistle stalks where they consume the pith. A single stalk may contain as many as a dozen or more larvae. The larvae excavate a gallery that can extend nearly the entire length of the stalk. They eject frass outside the stalk from holes that are periodically bored through the stalk. The hole are usually made just above a node or above where the stalk branches. The last-instar larvae leave the stalk and pupate in cocoons that are spun under the leaves and below the thistle head. The cocoons are spindle-shaped and are spun beneath a sheet of protective silk. |
| Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants. |