Thrinax

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Selandriinae
Tribe: Strongylogastrini
Genus: Thrinax Konow, 1885
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 Selandriinae subfamily are relatively small and slender. The range of Selandriinae is worldwide, it occurs on all continents except Antarctica (Goulet 1992). It is the most common and diverse group of tenthredinids in tropical regions, particularly in Central America, South America, and Southeast Asia (Smith 1969e). Selandriinae contains the only known sawflies that feed on non-vascular plants, specifically ferns (Smith et al. 2013).The subfamily can be distinguished from other subfamilies by wing venation (Goulet 1992).

Thrinax are medium-sized, about 7 mm in length, and generally black and white in color with orange/red legs. The genus is fern-feeding (Smith 1969e).

Diversity

There are 27 described extant species worldwide. Four occur in North America (Taeger et al. 2010).

A key to Nearctic species of Thrinax (as Hemitaxonus) is included in Smith 1969e.

Diagnostic characteristics

Subfamily characters

Genus characters

May be confused with

Thrinax can be confused with similar species in the subfamily Selandriinae or tribe Strongylogastrini. It can be distinguished from most other genera by the perpendicular anal crossvein, from closely related Eriocampidea by slender antennae and presence of occipital ridge, and from closely related Strongylogaster by the length of the pedicel (Smith 1969e).

Exotic pest species of concern

none

Host associations

In North America, Thrinax feeds on ferns, including Athyrium (lady fern), Athyrium thelypteroides (silver glade fern), Onoclea sensibilis (sensitive fern), Osmunda, Pteridium (bracken fern), and Matteuccia (ostrich fern) (Smith 1966a, Goulet 1992).

Life history

Specific biology of this genus is not known. Female Thrinax lay eggs onto the upper side of the leaf in groups up to 12 per leaf. Larvae feed externally and then overwinter in wood or pith of a nearby plant (Smith 1969e).

Distribution

World: This genus is known from North America and East Asia (Taeger et al. 2010). One species occurs in Europe (Blank 2002).

North America: Three species of Thrinax are eastern in distribution, found in eastern Canada and in the United States east of the Mississippi River. Thrinax primaria occurs in British Columbia, Oregon, and California (Smith 1969e).

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

Details about data used for maps can be found here.

Thrinax dubitata female lateral habitus; photo by J. Orr, WSDA

Thrinax dubitata female lateral habitus; photo by J. Orr, WSDA

Thrinax dubitata male lateral habitus; photo by J. Orr, WSDA

Thrinax dubitata male lateral habitus; photo by J. Orr, WSDA

Thrinax dubitata male dorsal habitus; photo by J. Orr, WSDA

Thrinax dubitata male dorsal habitus; photo by J. Orr, WSDA

Thrinax dubitata male face; photo by Q. Baine, WSDA

Thrinax dubitata male face; photo by Q. Baine, WSDA

Thrinax dubitata wings; photo by J. Orr, WSDA

Thrinax dubitata wings; photo by J. Orr, WSDA