Family common name: common sawflies
Genus: Fenusella Enslin, 1912
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).
Fenusella are generally small, about 3.5–4 mm in length, and most species are black with white markings; F. populifoliella is yellow with black markings (Smith 1971a). The Fenusini tribe are all leaf miners (Goulet 1992).
Fenusella can be confused with other genera in the subfamily, especially similar genus Metallus. It can be distinguished by the bifid tarsal claw, antennal pedicel width, and lack of a completely haired mesonotum (Smith 1967c, Goulet 1992).
Fenusella wuestneii and F. septentrionalis are leaf-mining pests of willow in Europe (Liston 2007).
Fenusella species in North America feed on Populus nigra (black poplar), Populus fremontii (Fremont cottonwood), Populus canadensis (Carolina poplar), Populus tremuloides (quaking aspen), and Populus balsamifera (balsam poplar) (Smith 1971a, Lotfalizadeh et al. 2017). Fenusella nana feeds on Betula papyrifera (paper birch) (Digweed et al. 2009), and F. alaskana feeds on Salix spp. (willow) (Smith 1971a).
Females oviposit into the edge of the leaf near the main lateral veins. After hatching, larvae feed on the inner leaf tissue and create blotch mines. They feed for about one month, and then at maturity, the larvae exit the mines and fall to the soil to build a cell, then burrow and overwinter. Fenusella are univoltine (Digweed et al. 2009, Lotfalizadeh et al. 2017).
Fenusella hortulana is an introduced pest species commonly known as the poplar tree blotch leaf-miner. It is recorded as causing extensive damage on poplar plantations in central and eastern Europe (Georgiev 2006), Turkey, and Iran. When present in high populations, F. hortulana can completely defoliate trees (Lotfalizadeh et al. 2017). Fenusella nana is another introduced pest known as the early birch leaf edgeminer. The characteristic mines are narrow at the edge of the leaf and expand to a large blotch mine near the center (Digweed et al. 2009).
North America: Fenusella occurs throughout the northern United States and southern Canada, extending south into Colorado and California in the west, as far north as Alaska (Smith 1971a). Fenusella nana is a Palearctic species that was first collected in North America in New York and Maine in 1966, and is now recorded throughout eastern Canada and in British Columbia and Washington (Digweed et al. 2009).
Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Fenusella
Details about data used for maps can be found here.