Lagium

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Tenthredininae
Tribe: Tenthredinini
Genus: Lagium Konow, 1904
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 Tenthredininae subfamily are relatively large compared to others in the family, often with distinct colorful markings. Some are wasp-like with black and yellow stripes (Goulet 1992). Many species’ life histories are not known. Some Tenthredininae species feed uniquely, as adults, on flower pollen and other insects (Smith 1993). They can be distinguished from other subfamilies by wing venation (Goulet 1992).

Lagium is a small genus of relatively large sawflies (13–16 mm). Lagium atroviolaceum in North America can be recognized by the size, black body, and completely darkened wings (Smith 1986b).

Diversity

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

Diagnostic characteristics

Subfamily characters

Genus characters

May be confused with

Lagium can be confused with similar species in the subfamily Tenthredininae. It can be distinguished from most other genera by the angle on the posteroventral area of metepimeron, the location of the fore wing anal crossvein, and the relatively long postnotum (Goulet 1992).

Exotic pest species of concern

none

Host associations

Lagium larvae feed on Sambucus (elderberry), including S. canadensis (American black elderberry), and Viburnum (Smith 1986b, Smith 1994b).

Life history

The specific biology of L. atroviolaceum is not known. The larva is relatively large, about 3 cm at maturity, and somewhat distinctive. The body color is dull gray with numerous orange and black short, stout tubercles, and some short spines along the dorsum (Smith 1994b).

Distribution

World: One species is North American, the other, Lagium apicale, occurs in China (Wei et al. 2006, Taeger et al. 2010).

North America: Lagium atroviolaceum occurs in eastern North America, from New Brunswick through New England and the Great Lakes region, south to Louisiana and Georgia (Smith 1986b).

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

Details about data used for maps can be found here.

 

Lagium atroviolaceum female lateral habitus; photo by J. Orr, WSDA

 

Lagium atroviolaceum female lateral habitus; photo by J. Orr, WSDA

Lagium atroviolaceum female dorsal habitus; photo by J. Orr, WSDA

Lagium atroviolaceum female dorsal habitus; photo by J. Orr, WSDA

Lagium atroviolaceum female face; photo by Q. Baine, WSDA

Lagium atroviolaceum female face; photo by Q. Baine, WSDA

Lagium atroviolaceum male lateral habitus; photo by J. Orr, WSDA

Lagium atroviolaceum male lateral habitus; photo by J. Orr, WSDA

Lagium atroviolaceum male dorsal habitus; photo by J. Orr, WSDA

Lagium atroviolaceum male dorsal habitus; photo by J. Orr, WSDA

Lagium atroviolaceum male face; photo by Q. Baine, WSDA

Lagium atroviolaceum male face; photo by Q. Baine, WSDA

Lagium atroviolaceum fore wing; photo by J. Orr, WSDA

Lagium atroviolaceum fore wing; photo by J. Orr, WSDA