Family common name: common sawflies
Genus: Kerita Ross, 1937
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).
Nematinae is the second-largest subfamily of Tenthredinidae, with over 1,250 species (Prous et al. 2014). They are most diverse in northern Eurasia and North America; only a few species occur in the Southern Hemisphere. Nematinae sawflies have a variety of feeding habits including external leaf feeding, leaf mining, and gall forming, and feed on a variety of hosts (Smith 2003b).
The Nematinae have been subject to numerous revisions in recent years. As of 2021, there are no comprehensive keys to many of the North American species of Nematinae (Prous et al. 2014). Because of changing taxonomy and extreme variability in morphology, identifying genera and species in the Nematinae may be more challenging than in other subfamilies of Tenthredindae. For this reason, knowing the host or behaviors of a specimen can be extremely helpful for identification within this subfamily.
Kerita is a rare genus of small sawflies, about 3.5–4 mm in length. Most species are black with light yellow legs (Smith 1976b).
There are three described species worldwide, and all occur in North America (Taeger et al. 2018).
A key to species is included in Smith 1976b.
Kerita may be confused with other genera in the subfamily Nematinae—especially those with fore wing vein 2r-rs present and vein 2m-cu meeting cell 2Rs—but can be distinguished from most genera by the incomplete hind wing vein 2A (some species of Pristiphora also have this vein incomplete, but can be distinguished by their indistinct notauli). Kerita can be distinguished from the closely related genus Pseudodineura by the postocular region of the head lacking fine pits (Goulet 1992) and by the position of the ocelli.
Larvae are leaf miners (Smith 1976b). When disturbed, Pseudodineurini larvae secrete the compound citral, which repels ants. This is presumably a beneficial defense strategy when they leave the mine to overwinter or pupate in the soil (Boevé et al. 2009).
World: The genus is known only from North America (Goulet 1992).
North America: Kerita fidala occurs in the Midwest, with records in Illinois and Indiana, and in Virginia (Smith 1976b, Smith 2009). Kerita atira and K. difala occur in the west from California north to British Columbia and Alberta, east to Utah (Smith 1976b).
Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Kerita
Details about data used for maps can be found here.