Stem miner (Lepidoptera: Gracillariidae) in Thalictrum

Record Details

Record no.:	0573
Feeding guild:	Stem miner
Taxonomy:	Lepidoptera: Gracillariidae: cf. Marmara
Stages observed:	trace, larva
Hosts in Thalictrum:	T. dioicum (early meadow rue)

I found a young larva mining a stem of the host in early July. The linear mines were long, narrow, and winding with a brown discoloration and a central line of black frass.

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the very narrow mines runs approximately parallel to the long axis of the stem for some distance, then winds across the width of the stem and around to the other side — Image #: 573-11 Stem mine.

two segments of the thin brown mine cross each other and then diverge — Image #: 573-01 Stem mine.

the mine terminates in a rounded end with the small transparent larva feeding there — Image #: 573-02 Stem mine, backlit, with larva at far right (larger version)

the sides of the larva's flat body are scalloped in outline — Image #: 573-03 Larva in mine.

the larva's head is shaped like a half-circle with two longitudinal lines in the middle and a pair of small curved mandibles in the front — Image #: 573-04 Larva.

the mine segments crisscross one another and wrap around the stem — Image #: 573-06 More views of a stem mine.

the feeding lines are tiny concentric arcs showing where the larva's mandibles scraped away the plant tissue — Image #: 573-07 Detail, stem mine; feeding lines within the mine are faintly visible in one area.

segments form a stretched out X shape and the central frass line is visible in both — Image #: 573-08 Detail, stem mine at a point where two segments of the mine cross.

Page created: February 4, 2026. Last update: none