Birch Sawfly
Arge pectoralis
This record describes Arge pectoralis (species). Recorded family: Argidae. Recorded order: Hymenoptera.
Identification and Appearance
Adult is said to be blue-black with white markings on legs (Connecticut Agricultural Experiment Station) the most commonly encountered argid ( 3 )
Wikipedia reference for Arge pectoralis: http://en.wikipedia.org/wiki/Arge_pectoralis.
Classification
- Kingdom
- Animalia
- Phylum
- Arthropoda
- Class
- Insecta
- Order
- Hymenoptera (Ants, Bees, Wasps and Sawflies)
- Family
- Argidae (Argid Sawflies)
- Genus
- Arge
Imported taxonomy record. Source availability varies; see the source references and editorial policy below.
Habitat and Range
Geographic Range
Transcontinental in Canada and n. US south to NC-MS-KS-CO-WA
Seasonal Activity
adults Jun-Jul, larvae Jul-Sep
Diet and Behavior
Diet: Larvae feed on birch ( Betula ), also hazelnut ( Corylus ), and alder ( Alnus ). Older references claiming that this species feeds on willow ( Salix ) require confirmation (C. Eiseman, pers. comm.).
Life History
Female deposits eggs in slits cut in the margin of leaves. Overwinters as last-instar larva inside a cocoon spun on leaf litter.
Additional species information
Species notes from the sources
Etymology: Arge pectoralis ( Leach 1817) Latin pectoralis means having a distinctive thorax
About Flies: the wider group
Order-level background for Hymenoptera, the group containing Arge pectoralis. Species-specific details appear above.
Group overview
Hymenoptera includes over 150,000 described species of ants, bees, wasps, and sawflies. Earth harbors approximately 20 quadrillion (20×10^15) ants, with a combined biomass of ~12 megatons of dry carbon - exceeding the combined biomass of all wild birds and mammals (PNAS, 2022).
Ecological role of the group
About 35% of the world's food crops depend on animal pollinators. The chocolate industry, valued at over $100 billion, depends on pollinating flies and midges. Ants are the dominant soil engineers in most terrestrial ecosystems, turning more soil than earthworms in many habitats.
Economic and practical significance of the group
Pollinators contribute $235-577 billion worth of annual global food production (FAO). In the U.S., bee pollination alone benefits crops valued at $18 billion annually, and honey bees are responsible for $5.4 billion in agricultural productivity. Between April 2023-2024, 55.1% of managed honey bee colonies were lost. The U.S. bee population dropped from 5 million to 2.5 million.
Recorded sources for this group: FAO, USDA, EPA, PNAS (2022), US Fish & Wildlife Service. Imported estimates may describe particular regions or reporting periods.
Photos of Birch Sawfly (3)
Photo credits: Contributed by Cotinis; Additional contributions by Joshua Stuart Rose , Chuck Entz , ceiseman , v belov
Frequently Asked Questions About Birch Sawfly
What is Birch Sawfly?
Birch Sawfly (Arge pectoralis) is a species in the family Argidae, within the order Hymenoptera.
How big is Birch Sawfly?
♂ 7.5-9.5 mm, ♀ 9.0-11.5 mm ; last instar larvae ~18 mm
How do you identify Birch Sawfly?
Adult is said to be blue-black with white markings on legs (Connecticut Agricultural Experiment Station)
Where is Birch Sawfly found?
Range: Transcontinental in Canada and n. US south to NC-MS-KS-CO-WA
What does Birch Sawfly eat?
The diet of the Birch Sawfly includes Larvae feed on birch ( Betula ), also hazelnut ( Corylus ), and alder ( Alnus ). Older references claiming that this species feeds on willow ( Salix ) require confirmation (C. Eiseman, pers. comm.)..
When is Birch Sawfly active?
Birch Sawfly: seasonal activity - adults Jun-Jul, larvae Jul-Sep.
What is the life cycle of a Birch Sawfly?
Female deposits eggs in slits cut in the margin of leaves. Overwinters as last-instar larva inside a cocoon spun on leaf litter.