Ametastegia

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Allantinae
Tribe: Empriini
Genus: Ametastegia Costa, 1882
Subgenera: Ametastegia, Protemphytus

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).

Sawflies in the Allantinae subfamily are mostly black and shining, sometimes with other colors. They have agricultural importance as some species are pests on cultivated and ornamental plants (Smith 1979a). They can be distinguished from other subfamilies by wing venation (Smith 2003a).

Ametastegia are small to medium-sized, about 5–8 mm in length. They are mostly black in color, sometimes with orange or lightly-colored sclerites on the thorax and abdomen (Khayrandish et al. 2015).

Diversity

There are 56 described extant species worldwide. Sixteen occur in North America (Smith 2003a, Taeger et al. 2010).

A Nearctic key to species is included in Smith 1979a.

Diagnostic characteristics

Subfamily characters

Genus characters​

May be confused with

Ametastegia can be confused with similar species in the subfamily Allantinae or tribe Empriini. It can be distinguished by the perpendicular anal crossvein, the shallowly notched clypeus, and the lack of hind wing cell M (Smith 1979a).

Exotic pest species of concern

none

Host associations

In North America, Ametastegia feeds on Rumex crispus (curly dock), other Rumex (dock), Polygonum erectum (upright knotweed), other Polygonum (knotweed), Viola (violet, pansy), and Salix (willow) (Smith 1979a, Smith 2003a).

Life history

The female Ametastegia lays eggs on the underside of a leaf along a vein (Carrillo et al. 1990). Larvae of A. glabrata are light green dorsally with pale longitudinal stripes (Malipatil et al. 1995). Larvae of other species are less well-known. The young larvae feed singly on the underside of the leaf, leaving a series of large circular holes (Carrillo et al. 1990). At maturity the prepupae search for a desired plant medium in which to burrow and create a cell. This can be a fruit, a stem, the pith of a berry cane, a corn stalk, decaying wood, or even tree bark. Often the plant used for creating the pupal cell is not the larval host and as such is considered a secondary host. Many species are bi- or multivoltine (Smith 1979a, Malipatil et al. 1995).

Though the larvae do not feed on fruit, the prepupae of A. glabrata, known as the dock false-worm (Malipatil et al. 1995), is recorded using apples as a secondary host to pupate. The damage inflicted on the apple is sufficient to give this species pest status (Newcomer 1916, Smith 1979a). In other locations outside of North America, the damage inflicted by A. glabrata on raspberry canes and grape vine is also significant (Carrillo et al. 1990, Malipatil et al. 1995, Khayrandish et al. 2015).

Distribution

World: This genus is known from North America, central and southern Europe east to Siberia, including Iceland, and in western Asia including Iran (Smith 1979a, Khayrandish et al. 2015). Ametastegia glabrata has been introduced to Chile, discovered in 1987 (Carrillo et al. 1990), and to Australia, discovered in 1993 (Malipatil et al. 1995).

North America: Ametastegia is widespread and recorded throughout North America, as far north as Alaska and the Yukon Territory, and in Mexico and Central America, as far south as Costa Rica (Smith 1979a, Smith 2003a). A few larval specimens have been collected in Greenland (Vilhelmsen 2015).

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

Details about data used for maps can be found here.

Ametastegia glabrata female lateral habitus; photo by J. Orr, WSDA

Ametastegia glabrata female lateral habitus; photo by J. Orr, WSDA

Ametastegia pallipes female dorsal habitus; photo by J. Orr, WSDA

Ametastegia pallipes female dorsal habitus; photo by J. Orr, WSDA

Ametastegia tenera female face; photo by Q. Baine, WSDA

Ametastegia tenera female face; photo by Q. Baine, WSDA

Ametastegia tenera male dorsal habitus; photo by J. Orr, WSDA

Ametastegia tenera male dorsal habitus; photo by J. Orr, WSDA

Ametastegia tenera male face; photo by Q. Baine, WSDA

Ametastegia tenera male face; photo by Q. Baine, WSDA

Ametastegia tenera wings; photo by P. Jones, WSDA

Ametastegia tenera wings; photo by P. Jones, WSDA