Nematinus

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Nematinae
Tribe: Nematini
Genus: Nematinus Rohwer, 1911
Subgenera: none

Background

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.

Nematinus are about 5–8 mm in length and usually mostly orange with black markings (Smith 1986c).

Diversity

There are 27 described species worldwide. Four occur in North America (Taeger et al. 2018).

A key to North American females of species of Nematinus is included in Smith 1986c.

Diagnostic characteristics

Subfamily characters​

Genus characters​

May be confused with

Nematinus may be confused with other genera in the subfamily Nematinae—especially Euura and Nematus—but females can be distinguished by the dorsally wide ovipositor sheath and enlarged ninth abdominal segment, while males can be distinguished from all but some species of Euura by the combination of symmetrical mandibles, incomplete fore wing vein 2A+3A, vein 2m-cu joining cell 1Rs, and the long inner tooth of the tarsal claw (Goulet 1992).

Exotic pest species of concern

none

Host associations

Nematinus feeds on species of Alnus (alder) and Betula (birch) (Goulet 1992), including Betula papyrifera (paper birch) (Smith 1986c).

Life history

Larvae feed singly on the underside of the leaf, at first just on the parenchyma, then as it develops, on the entire leaf. At maturity, the larvae fall to the ground and spin a cocoon in which to overwinter. Nematinus is univoltine (Smith 1986c).

Distribution

World: The genus is known from North America, throughout Europe and in Morocco, Siberian Russia, and Japan (Smith 2017b, Taeger et al. 2018).

North America: Nematinus occurs in the northern United States and Canada, and in Alaska (Smith 1986c).

Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Nematinus

Details about data used for maps can be found here.

Nematinus acuminatus female lateral habitus; photo by J. Orr, WSDA

Nematinus acuminatus female lateral habitus; photo by J. Orr, WSDA

Nematinus acuminatus female dorsal habitus; photo by J. Orr, WSDA

Nematinus acuminatus female dorsal habitus; photo by J. Orr, WSDA

Nematinus acuminatus female face; photo by Q. Baine, WSDA

Nematinus acuminatus female face; photo by Q. Baine, WSDA

Nematinus luteus male lateral habitus; photo by J. Orr, WSDA

Nematinus luteus male lateral habitus; photo by J. Orr, WSDA

Nematinus luteus male face; photo by Q. Baine, WSDA

Nematinus luteus male face; photo by Q. Baine, WSDA