Identification
Adult Markings: In this species that palps are whitish and the head tuft is tawny but heavily dusted with blackish scales. The thorax and ground color of the forewing have a mixture of yellowish-brown, yellowish-golden and dark-brown to blackish scales that are weakly organized to form a coarsely mottled appearance. A series of lustrous silvery-gray strigulae and spots are either embedded in these or organized as costal strigulae. The lighter blotches and scales are most prevalent on the dorsal half of the wing. The costa has a pair of posteriorly oblique antemedial strigulae that are located between a dark brown medial costal spot and a similar antemedial costal spot at around one-fourth the wing length. The strigulae tend to run parallel to each other, are sometimes fused along their lengths, and usually terminate near the center of the wing. Other silvery- gray costal lines are present immediately basal to the antemedial costal spot, immediately posterior to the medial spot, and as one or two poorly developed lines on the apical fourth of the costa that run towards a diffuse, blackish postmedial bar. Most of the costal strigulae have white scales at the costal margin, and the fringe has a series of blackish blotches and a well-defined black basal line. The hindwing is medium to dark brown with a whitish fringe that has a dark basal line. Pristerognatha agilana is sometimes confused with Olethreutes auricapitana . A key distinction is that the two silvery antemedial lines of O. auricapitana fuse to form a āVā that terminates about one-third of the way between the costa and the dorsal margin. The two lines tend to run parallel to one another, often remain separate, and extend much farther inward in P. agilana . The former also has a silvery spot above the V near the dorsal margin (absent in P. agilana ), along with golden colored palps and head tufts, versus more whitish palps and blackish head tufts for P. agilana .
Forewing Length: 4.5-7.0 mm (Gilligan et al., 2008).
Structural photos
Adult ID Requirements: Identifiable from good quality photos of unworn specimens.
Immatures and Development: The larvae are borers that feed inside the stems and root bases of jewelweeds. Based of specimens collected in Iowa (BugGuide) and North Carolina, each stem typically houses a single larva. The larvae appear to feed first in the stems -- most commonly in the lower half -- then work their way to the swollen root bases. Infected plants have dark brown to brownish-black frass that can often be detected by holding the stem up to bright light. In Iowa, the larvae overwinter in the dead stems and root bases where they form a plug at both ends of the stem or root base before pupating in the spring. In North Carolina, both larvae and pupae have been found inside the root bases in mid-August, which suggests that overwintering can occur in either stage. Local emergence is presumably tied to when jewelweeds are moderately large, and infected plants often appear wilted even when growing in wet soils. Larvae have been found in North Carolina using both of our native species of Impatiens . The older larvae have whitish to dull cream-colored bodies, a dark brown or brownish-black head, and a dull yellowish prothoracic shield.
Larvae ID Requirements: Identifiable from good quality photos, especially where associated with known host plants.
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