Family common name: common sawflies
Genus: Metallus Forbes, 1885
The Tenthredinidae are the most species-rich family and are found throughout the world, in all continents but Antarctica. They are known as the “common sawflies.” They can generally be recognized by a cylindrical body and long, segmented antennae. Otherwise, they come in a variety of colors, sizes, and forms (Goulet 1992).
Sawflies in the Heterarthrinae subfamily are generally small and dark-colored. Many species of this family are economic pests of trees and shrubs and can be characterized by their skeletonizing or leaf-mining larval feeding behaviors. Heterarthrinae adults can be distinguished from those of other subfamilies by wing venation (Smith 1971a).
Metallus can be confused with other genera in the subfamily, especially similar genus Fenusella. It can be distinguished by the bifid tarsal claw, antennal pedicel width, and haired mesonotum (Smith 1967c, Goulet 1992). The males have distinctly widened and flattened third and fourth antennal segments (Smith 1971a).
Females oviposit into the upper surface of a leaf. After hatching, larvae feed on the inner leaf tissue and create blotch mines, which sometimes combine into one because they are not able to establish mines on new leaves. At maturity, the larvae exit the mines and fall to the soil to build a cell, then burrow and pupate, or overwinter. (Eiseman and Smith 2017). Other Fenusini larvae lack larval prolegs, but prolegs are present on Metallus abdominal segments 2–7 and 10 (Smith 1971a). The species native to North America are univoltine or bivoltine (Eiseman and Smith 2017).
North America: Metallus occurs throughout the northern United States and southern Canada, as far south as Oregon in the west, and Virginia in the east (Smith 1971a). One introduced species, M. lanceolatus, was first collected in British Columbia in 1933, then in several northeastern states and provinces in the 1960s, and is now also recorded from Washington (Looney et al. 2016).
Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Metallus
Details about data used for maps can be found here.