Family: Tenthredinidae
Family Common Name: Common Sawflies
Subfamily: Allantinae
Tribe: Empriini
Genus: Phrontosoma MacGillivray, 1908
Subgenera: none


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).

Phrontosoma are medium-small in size, about 5–7 mm in length. All North American species are mostly black or black with orange thoracic sclerites (Smith 1979a).


There are three described extant species worldwide, and all are Nearctic (Taeger et al. 2010).

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

Diagnostic characteristics

Subfamily characters

Genus characters​

May be confused with

Phrontosoma can be confused with similar species in the subfamily Allantinae or tribe Empriini. It can be distinguished by the combination of a short genal ridge, shallow clypeal emargination, and bidentate mandibles (Smith 1979a).

Exotic pest species of concern


Host associations

In North America, Phrontosoma usta feeds on Cornus sp. (dogwood). No hosts are recorded for other species (Smith 1979a).

Life history

The biology of Phrontosoma is unknown. Other genera in the subfamily feed on leaves and pupate in the soil (Smith 1979a).


World: This genus is known only from North America (Taeger et al. 2010).

North America: All species of Phrontosoma occur commonly in the northeastern United States and eastern Canada. There are additional collections of P. belfragei in Texas and in Alberta. Phrontosoma brocca has also been collected in Corvallis, Oregon (Smith 1979a).

Map data from: (29 October 2019) GBIF Occurrence Download Phrontosoma

Details about data used for maps can be found here.

Specimens of this species not available for imaging.