Other Common Names
Hemlock Moth
Defoliating Hemlock Moth (name used in the weed control industry)
Synonyms and other taxonomic changes
Phalaena alstromeriana Clerck 1759
Agonopterix alstroemeriana (Clerck) 1759
*
Note: The specific epithet is commonly spelled (in Europe) with a single "e" -
alstromeriana (see
funet.fi)
Identification
Adult: forewing creamy or pale brown with whitish area at base and a large dark squarish blotch that touches the costa mid-way along the wing; a short broken dark line runs obliquely just above the blotch; a few dark spots usually present along the wing fringe, and several small dots may be scattered across the wing.
Larva: changes color and markings as it matures, from clear whitish-yellow (early instars) to black-dotted greenish (late instars). See
detailed description by Ian Smith.
Image of late instar larva:

Range
Northeastern US and southeastern Canada, plus northwestern US and southwestern Canada; spreading inland from both regions
Native to Europe
Habitat
Fields, roadsides, waste places - wherever the host plant (Poison Hemlock) occurs; adults attracted to artificial light
Season
Adults fly from April to August
Larvae from May to July
Food
Larvae feed only on Poison Hemlock (Conium maculatum), which was introduced to North America from Europe in the 1800s
Remarks
First recorded in North America in New York State in 1973; accidentally introduced to the US northwest shortly after, and has since spread rapidly from both locations.
Larvae of this species are commercially available for biological control of Poison Hemlock.
The common name of Poison Hemlock Moth is preferable to Hemlock Moth or Defoliating Hemlock Moth because this species feeds solely on the herbaceous plant Poison Hemlock (Conium maculatum), and has no association with the coniferous trees called Hemlock (Tsuga spp.).
Print References
Berenbaum, M. R., & S. Passoa (1983). Notes on the biology of
Agonopterix alstroemeriana (Clerck), with description of the immature stages (Oecophoridae). J. Lepid. Soc. 37:38-45 (
Full Text)
Berenbaum, M. R., and T. L. Harrison (1994).
Agonopterix alstroemeriana (Oecophoridae) and other lepidopteran associates of poison hemlock
(Conium maculatum) in east central Illinois. Great Lakes Entomol. 27: 1-5 (Full Text on pages 4-8 of
PDF here)
Castells, Eva & M. R. Berenbaum (2006). Laboratory Rearing of
Agonopterix alstroemeriana, the Defoliating Poison Hemlock (
Conium maculatum L.) Moth, and Effects of Piperidine Alkaloids on Preference and Performance. Environmental Entomology, 35(3): 607–615. (
Full Text)
McKenna, D. D., A. R. Zangerl., and M. R. Berenbaum (2001). A native hymenopteran predator of
Agonopterix alstroemeriana (Lepidoptera: Oecophoridae) in East-Central Illinois. Great Lakes Entomol. 34: 71-75. (
Full Text)
Powell, J. A., & S. Passoa (1991). Rapid colonization of the western United States by the Palearctic moth,
Agonopterix alstroemeriana (Oecophoridae). J. Lepid. Soc. 45:234-236. (
Full Text)
Internet References
Live images from UK Moths (Full-size:
3 larval instars (Ian Smith);
Adult (Ian Kimber)
Live larvae, adult, and feeding damage images by Eric Coombs, Oregon Dept. Agriculture (from InsectImages.org).
Lepiforum German website (many good images!). ["Google Translate" of the page to English
here]
Pinned adult image (B. Gustafsson, Sweden)