Wingspan 17-20 mm.
Reasonably common in England and Wales, becoming less so into Scotland. Also recorded in southern Ireland.
One of the more distinctive Agonopterix species, with its combination of well-marked purplish-brown forewings and buffish thorax and head.
The larva feeds on St. Johns-wort (Hypericum spp.), spinning together the shoots and feeding within.
The normal flight period for the adults is July to August, when the species is attracted to light.
Larva: (description Ian F. Smith)
Foodplant: May - June in spun shoots of Hypericum spp.
Length: 13 mm described.
Head: Yellowish brown. Dark brown posterolateral mark. Stemmata linked by black curved mark.
Prothoracic shield: Translucent tinted yellowish brown, mixed with greenish colour of body when head extended. Divided by a dark-edged paler medial line, which is flared at posterior, and does not quite reach the anterior.
Thoracic legs: Translucent yellowish brown.
Body: Whitish grey-green with a silky sheen. Contractile vessel shows as dark green dorsal line.
Spiracles: Black. Prothoracic spiracle large, and obvious as only black mark on T1.
Pinacula: Small. Black. Largest on dorsum of A9.
Anal plate: Translucent tinted yellowish brown, showing green of body.
Prolegs: Yellowish. Large lateral sclerite on anal proleg; yellowish brown translucent (showing green).
Lathronympha strigana makes a similar spinning on Hypericum spp, but its prothoracic shield is black.