Xyela

Taxonomy

Family: Xyelidae
Family common name: xyelid sawflies
Subfamily: Xyelinae
Tribe: Xyelini
Genus: Xyela Dalman, 1819
Subgenera: Xyela, Mesoxyela, Pinicolites

Background

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

Xyela adults are small, less than 5 mm in length. They are somewhat common and the most species-rich genus in the Xyelidae. Xyela feed as larvae and adults, generally on the protein-rich pollen of male pine flowers (Smith 1990, Blank et al. 2013, Blank and Kramp 2017).

Diversity

There are 49 described extant species worldwide, restricted to the Northern Hemisphere. Twenty species occur in North America (Taeger et al. 2010, Blank et al. 2017).

A key to the North American species of Xyela is included in Burdick 1961.

Diagnostic characteristics

May be confused with

Xyelidae can be distinguished from other sawfly families by the long ovipositor and the characteristic elongate third antennal segment which is wider than the remaining flagellum. Xyela can be confused with other species in the genus. It can be distinguished by the number of antennal segments, the wing venation, and small body size (Burdick 1961, Goulet 1992).

Exotic pest species of concern

None. While Xyela feeds on an economically significant plant family, the feeding behavior of the larvae does not noticeably damage the tree (Burdick 1961).

Host associations

Larvae feed exclusively on Pinus (pine) species. In North America, the recorded host species are P. contorta (lodgepole pine), P. cembra (Swiss pine), P. strobus (eastern white pine), P. ponderosa (ponderosa pine), P. sabiniana (foothill pine), P. virginiana (Virginia pine), P. palustris (longleaf pine), P. elliottii (slash pine), P. monophylla (singleleaf pinyon), P. taeda (loblolly pine), P. echinata (shortleaf pine), P. mugo (mountain pine), P. coulteri (Coulter pine), P. muricata (bishop pine), P. banksiana (jack pine), P. radiata (Monterey pine), and P. jeffreyi (Jeffrey pine) (Smith 1978, Blank and Kramp 2017). All Old-World species and the majority of North American species are monophagous (Blank et al. 2017).

Adults feed on pollen from many sources, including Salix sp. (willow), Alnus sp. (alder), and Betula sp. (birch) (Smith 1990).

Life history

The female uses the elongate ovipositor to deposit eggs into developing male cones. Emerged larvae begin to feed on only pollen inside pollen sacs at the base of the sporophylls, and consuming the sporophylls as the larvae mature. Though they live inside the cone, they are not borers, and instead move among the sporophylls as the cone grows and opens. The larvae usually reach maturity right before the time of pollen dispersal from the cone, where they then fall to the ground to overwinter and pupate (Burdick 1961, Yates and Smith 2009).

One rare species, X. gallicaulis, does not feed inside the cones and instead is a gall-inducer of young pine shoots. The gall form is elongate and looks like a swollen shoot. Gall formation does not cause mortality of the growing shoot. The larva feeds on the stem tissue of the gall, then bores out of the gall to drop to the ground and pupate (Yates and Smith 2009).

Xyela is most often univoltine, with the exception of X. gallicaulis which has a life cycle of two years (Yates and Smith 2009). Adults also feed on pollen during their flight period (Greenbaum 1974).

Distribution

World: Xyela is widespread in Europe, Asia, and North America. (Taeger et al. 2010). One species is endemic to the island of Taiwan (Blank et al. 2017).

North America: The range of Xyela largely follows distributional patterns of pine forests. In North America, their range extends from the Sonoran and Chihuahua deserts of Mexico and southwest United States, north through the Rocky, Sierra, and Cascade Mountains in the west, almost all of western and southern Canada, through the northern Midwest, along the East Coast down through the Southeast (Burdick 1961).

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

Details about data used for maps can be found here.

Xyela sp. female lateral habitus; photo by J. Orr, WSDA

Xyela sp. female lateral habitus; photo by J. Orr, WSDA

Xyela sp. female dorsal habitus; photo by Q. Baine, WSDA

Xyela sp. female dorsal habitus; photo by Q. Baine, WSDA

Xyela sp. female face; photo by Q. Baine, WSDA

Xyela sp. female face; photo by Q. Baine, WSDA

Xyela bakeri male lateral habitus; photo by J. Orr, WSDA

Xyela bakeri male lateral habitus; photo by J. Orr, WSDA

Xyela bakeri male dorsal habitus; photo by J. Orr, WSDA

Xyela bakeri male dorsal habitus; photo by J. Orr, WSDA

Xyela bakeri male face; photo by J. Orr, WSDA

Xyela bakeri male face; photo by J. Orr, WSDA

Xyela bakeri wing; photo by J. Orr, WSDA

Xyela bakeri wing; photo by J. Orr, WSDA

Xyela bakeri male antenna; photo by J. Orr, WSDA

Xyela bakeri male antenna; photo by J. Orr, WSDA