Tethida

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Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Blennocampinae
Tribe: Tomostethini
Genus: Tethida Ross, 1937
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 subfamily Blennocampinae have a diverse set of life histories and habits. Many species are restricted to subtropical and tropical regions, but the genus is still fairly species-rich in North America. Blennocampinae includes many sawflies that feed on ornamental and forestry crops. This subfamily can be recognized by wing venation and bidentate mandibles (Smith 1969d).

Tethida is monotypic. Tethida barda is about 7 mm in length and mostly black with reddish coloring on the lateral thorax and darkened wings (Smith 1969d).

Diversity

There is a single described extant species worldwide, and it is North American (Taeger et al. 2018).

Diagnostic characteristics

Subfamily characters

• angle of intersection of fore wing veins Cu1 and 1m-cu between 120°–150° (Goulet 1992)
• fore wing veins 2A and 3A incomplete (Smith 1969d)

Genus characters

• basal fifth of the clypeus evenly haired (Goulet 1992)
• epicnemial area clearly outlined (Goulet 1992)
• fore wing veins M and 1m-cu narrowed at apex, not parallel (Smith 1969d)
• hind wing cell M present (Smith 1969d)
• mesonotum sparsely haired on central surface (Goulet 1992)
• pulvilli on the first and second tarsomeres well developed (Goulet 1992)
• tarsal claw appearing simple but with very small inner tooth (Smith 1969d)
• pits not present on mesoscutellum and mesepisternum (Goulet 1992)

May be confused with

Tethida can be confused with similar species in the subfamily Blennocampinae. It can be distinguished from most other genera by the developed pulvilli on basal tarsomeres and by the epicnemial area, and from similar genus Tomostethus by the sparsely haired mesonotum and the basal area of the clypeus (Goulet 1992).

Exotic pest species of concern

none

Host associations

Tethida barda feeds on species of Fraxinus (ash) (Goulet 1992), including F. americana (white ash) (Schlesinger 1990) and F. pennsylvanica (green ash) (Brakie 2013).

Life history

Tethida barda is a pest of ash trees known as the black-headed ash sawfly (Brakie 2013). Females oviposit into the edge of the leaves in rows, leaving a blistered patterning on the leaf. After hatching, larvae feed gregariously on the underside of the leaf, consuming it entirely. Larvae are white to light green with black head capsules (Osborne 1884).

Distribution

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

North America: Tethida barda occurs in the eastern part of North America, from as far north as New Brunswick and Saskatchewan, south to Florida and Texas (Smith 1969d).

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

Details about data used for maps can be found here.