Nefusa

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Heterarthrinae
Tribe: Fenusini
Genus: Nefusa Ross, 1951
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).

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).

Nefusa are generally very small, about 2–4 mm in length, and mostly black with slightly darkened wings (Smith 1971a, Wei 1994). It is monotypic in North America. Nefusa ambigua is mostly black with yellow on the venter of the abdomen, and on parts of the antennae and legs (Smith 1971a). The Fenusini tribe are all leaf miners (Goulet 1992).

Diversity

There are three described extant species worldwide. One species occurs in North America (Taeger et al. 2010).

Diagnostic characteristics

Subfamily characters

Genus characters​

May be confused with

Nefusa can be confused with other genera in the subfamily. It can be distinguished by the prepectus, antennal pedicel length, and haired mesonotum (Smith 1971a, Goulet 1992).

Exotic pest species of concern

none

Host associations

Nefusa in North America feeds on Viola sororia (common blue violet) and other Viola spp. (violet) (Smith and Eiseman 2015).

Life history

Females oviposit single eggs into the upper surface of the leaf. After hatching, larvae feed on the inner leaf tissue and create blotch mines for about 22-28 days (Smith 1971a). Larvae are white and dorsoventrally flattened with reduced thoracic legs and undeveloped prolegs (Smith and Eiseman 2015). At maturity, the larvae exit the mines and fall to the soil to build a cell, then burrow and overwinter (Smith 1971a). Nefusa ambigua is bivoltine (Smith and Eiseman 2015).

Distribution

World: This genus is known from North America, and from Fujian and Sichuan provinces of China (Wei 1994, Taeger et al. 2018).

North America: Nefusa ambigua occurs in eastern United States and southeastern Canada (Smith 1971a).

Map data from Smithsonian National Museum of Natural History Entomology Collection (USNM)

Details about data used for maps can be found here.

Nefusa ambigua female lateral habitus; photo by J. Orr, WSDA

Nefusa ambigua female lateral habitus; photo by J. Orr, WSDA

Nefusa ambigua female dorsal habitus; photo by J. Orr, WSDA

Nefusa ambigua female dorsal habitus; photo by J. Orr, WSDA

Nefusa ambigua female face; photo by Q. Baine, WSDA

Nefusa ambigua female face; photo by Q. Baine, WSDA

Nefusa ambigua male lateral habitus; photo by J. Orr, WSDA

Nefusa ambigua male lateral habitus; photo by J. Orr, WSDA

Nefusa ambigua male dorsal habitus; photo by J. Orr, WSDA

Nefusa ambigua male dorsal habitus; photo by J. Orr, WSDA

Nefusa ambigua ​male face; photo by Q. Baine, WSDA

Nefusa ambigua ​male face; photo by Q. Baine, WSDA

Nefusa ambigua fore wing; photo by J. Orr, WSDA

Nefusa ambigua fore wing; photo by J. Orr, WSDA