Pleroneura

Taxonomy

Family: Xyelidae
Family common name: xyelid sawflies
Subfamily: Xyelinae
Tribe: Pleroneurini
Genus: Pleroneura Konow, 1897
Subgenera: none

Background

Most phylogenies position Xyelidae as the most primitive family of all Hymenoptera. Most xyelids are associated with a primitive plant group, coniferous trees (Ross 1932, Blank and Kramp 2017).

Pleroneura adults are small, about 5–8 mm in length, and are fairly uncommon. They can be a pest on fir trees in regions where firs grow (Carleton et al. 2014).

Diversity

There are 12 described extant species worldwide, restricted to the Northern Hemisphere. Five species occur in North America (Taeger et al. 2010).

A key to North American species of Pleroneura is included in Smith et al. 1977.

Diagnostic characteristics

May be confused with

Xyelidae can be distinguished from other families by the long ovipositor, and the characteristic elongate third antennal segment that is wider than the remaining flagellum. Pleroneura can easily be confused with other genera in the family. It can be distinguished by the number of antennal segments, the wing venation, and maxillary palpus (Ross 1932, Goulet 1992).

Exotic pest species of concern

none

Host associations

Larvae feed exclusively on Abies (fir) species (Smith et al. 1977). In North America, the recorded host species are A. concolor (white fir), A. balsamea (balsam fir), and A. lasiocarpa (subalpine fir) (Smith et al. 1977, Smith 1978).

Life history

The female uses the elongate ovipositor to deposit eggs into unopened leaf buds. The leaf bud scales provide protection for the egg until it hatches (Ohmart and Dahlsten 1979, Carleton et al. 2014). After hatching, the larva feeds on the growth tip of a new young shoot, often leading to mortality of the shoot (Smith et al. 1977). Larvae are cylindrical, white, and stout; at maturity they measure 6–9 mm in length (Smith 1967b) and drop to the ground to overwinter and pupate (Ohmart and Dahlsten 1979, Carleton et al. 2014).

Distribution

World: Pleroneura occurs in North America, eastern and central Europe, and East Asia (Taeger et al. 2010).

North America: Four of the five species of North American Pleroneura occur west of the Rocky Mountains, from California north to British Columbia, as far east as Utah. The range of P. brunneicornis extends through New England, New York, and the eastern provinces of Canada; Nova Scotia, New Brunswick, and Quebec (Smith et al. 1977, Smith 1978, Taeger et al. 2010).

Map data from: GBIF.org (26 June 2019) GBIF Occurrence Download Pleroneura

Details about data used for maps can be found here.

Pleroneura californica female lateral habitus; photo by J. Orr, WSDA

Pleroneura californica female lateral habitus; photo by J. Orr, WSDA

Pleuroneura californica female dorsal habitus; photo by J. Orr, WSDA

Pleuroneura californica female dorsal habitus; photo by J. Orr, WSDA

Pleuroneura californica female face; photo by J. Orr, WSDA

Pleuroneura californica female face; photo by J. Orr, WSDA

Pleroneura californica male lateral habitus; photo by J. Orr, WSDA

Pleroneura californica male lateral habitus; photo by J. Orr, WSDA

Pleroneura californica male dorsal habitus; photo by J. Orr, WSDA

Pleroneura californica male dorsal habitus; photo by J. Orr, WSDA

Pleroneura californica male face; photo by J. Orr, WSDA

Pleroneura californica male face; photo by J. Orr, WSDA

Pleroneura californica fore wing; photo by Q. Baine, WSDA

Pleroneura californica fore wing; photo by Q. Baine, WSDA

Pleroneura californica antenna; photo by Q. Baine, WSDA

Pleroneura californica antenna; photo by Q. Baine, WSDA

Pleroneura californica female head; photo by Q. Baine, WSDA

Pleroneura californica female head; photo by Q. Baine, WSDA

Pleroneura californica female clypeus; photo by Q. Baine, WSDA

Pleroneura californica female clypeus; photo by Q. Baine, WSDA