Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada

Species Arge pectoralis - Birch Sawfly

Sawfly Larva - Arge pectoralis Birch Sawfly - Arge pectoralis (Argidae) - Arge pectoralis Birch Sawfly - Arge pectoralis (Argidae) - Arge pectoralis Yellow Caterpillar - Arge pectoralis Orange buttonbush bug - Arge pectoralis Unknown Sawfly - Arge pectoralis - female Chokecherry Sawfly - Arge pectoralis birch sawfly larva - Arge pectoralis
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon ("Symphyta" - Sawflies, Horntails, and Wood Wasps)
Family Argidae (Argid Sawflies)
Genus Arge
No Taxon (pectoralis group)
Species pectoralis (Birch Sawfly)
Explanation of Names
Arge pectoralis (Leach 1817)
Latin pectoralis means having a distinctive thorax
♂ 7.5-9.5 mm, ♀ 9.0-11.5 mm(1); last instar larvae ~18 mm(2)
Adult is said to be blue-black with white markings on legs (Connecticut Agricultural Experiment Station)
Transcontinental in Canada and n. US south to NC-MS-KS-CO-WA(1)
adults Jun-Jul, larvae Jul-Sep(2)
Larvae feed on birch (Betula), also hazelnut (Corylus), alder (Alnus), and willow (Salix)(2)
Life Cycle
Female deposits eggs in slits cut in the margin of leaves. Overwinters as last-instar larva inside a cocoon spun on leaf litter.(2)
the most commonly encountered argid(3)
Works Cited
1.The sawfly genus Arge (Hymenoptera: Argidae) in the Western Hemisphere
Smith D.R. 1989. Transactions of the American Entomological Society 115: 83-205.
2.Eastern Forest Insects
Whiteford L. Baker. 1972. U.S. Department of Agriculture · Forest Service.
3.Garden Insects of North America : The Ultimate Guide to Backyard Bugs (Princeton Field Guides)
Whitney Cranshaw. 2004. Princeton University Press.