Bidigitus

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Heterarthrinae
Tribe: Fenusini
Genus: Bidigitus D.R. Smith, 1967
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).

Bidigitus is monotypic. Bidigitus platani has a very small recorded range and is fairly uncommon. The adults are small, about 4 mm, and mostly black with white markings on the legs (Smith 1971a).

Diversity

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

Diagnostic characteristics

Subfamily characters

Genus characters

May be confused with

Bidigitus can be confused with other genera in the subfamily, especially the similar genus Profenusa. It can be distinguished by the bifid tarsal claw and the hind wing anal cell length to petiole length ratio (Smith 1967c, Smith 1971a).

Exotic pest species of concern

none

Host associations

Bidigitus platani feeds on Platanus racemosa (California plane tree) (Smith 1971a).

Life history

Females oviposit into the upper side of leaves in early spring. The hatched larvae feed gregariously inside the leaf on the parenchyma as leaf miners, creating blotch mines. The feeding stage lasts about 30 days, and when the larvae are mature, they fall to the ground and build cocoons in which to pupate, or they overwinter and then pupate. Because of this quick life cycle, this species is multivoltine with 3–5 generations in a single year (Smith 1971a).

Distribution

World: This genus is North American (Taeger et al. 2018).

North America: Bidigitus occurs in California, specifically the southern region of the state, with records in Santa Barbara and Anaheim (Smith 1971a).

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

Details about data used for maps can be found here.

Bidigitus platani female lateral habitus; photo by J. Orr, WSDA

Bidigitus platani female lateral habitus; photo by J. Orr, WSDA

Bidigitus platani female dorsal habitus; photo by J. Orr, WSDA

Bidigitus platani female dorsal habitus; photo by J. Orr, WSDA

Bidigitus platani female face; photo by Q. Baine, WSDA

Bidigitus platani female face; photo by Q. Baine, WSDA

Bidigitus platani male lateral habitus; photo by Q. Baine, WSDA

Bidigitus platani male lateral habitus; photo by Q. Baine, WSDA

Bidigitus platani male dorsal habitus; photo by J. Orr, WSDA

Bidigitus platani male dorsal habitus; photo by J. Orr, WSDA

Bidigitus platani male face; photo by Q. Baine, WSDA

Bidigitus platani male face; photo by Q. Baine, WSDA