Stem borer (Coleoptera: Erotylidae) in Osmorhiza

Record Details

Record no.:	0351
Feeding guild:	Stem borer
Taxonomy:	Coleoptera: Erotylidae: Acropteroxys gracilis
Stages observed:	trace, larva, adult
Hosts in Osmorhiza:	undetermined O. sp., O. claytonii or O. longistylis (sweet cicely, aniseroot)

I located several dead stems inhabited by overwintering mature or nearly mature larvae in April 2017, and another stem inhabited by an overwintering larva in February 2024. Adults from the 2017 batch emerged by mid-June.

Featured Images

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pale orange beetle larva stretched out in its tunnel in a dry stalk of Osmorhiza that has been split open for the photo — Image #: 351-01 Larva in stem. (Photo date: April 7, 2017)

the larva curls its body in the stem tunnel; it has a rounded head and sickle-shaped mandibles — Image #: 351-02 Larva in stem.

the larva has three thoracic segments and eight abdominal segments; its body color is pale pinkish-orange — Image #: 351-03 Larva in stem.

the plug of frass is several millimeters long, made of dry, compacted, irregularly shaped pellets, and the larva perches behind it in the stem with its head facing the plug — Image #: 351-04 Inhabited stem, showing plug of frass sealing off the open end.

very slender black beetle with red on the sides of the pronotum — Image #: 351-05 Reared adult, dorsal view. (Photo date: June 16, 2017)

the red color on the pronotum extends to the side and underside of the first thoracic segment and also to the underside of the head, while the rest of the thorax and the abdomen are black underneath — Image #: 351-06 Reared adult, lateral view.

Specimen Data for Images

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Coll. 04/04/17, photos of larva and stem damage on 04/07/17 (01-04), adults em. 06/13/17-~06/16/17, photos of adult on 06/16/17 (05-07).

Page created: February 5, 2026. Last update: none