Megaxyela

Taxonomy

Family: Xyelidae
Family common name: xyelid sawflies
Subfamily: Macroxyelinae
Tribe: Macroxyelini
Genus: Megaxyela Ashmead, 1898
Subgenera: none

Background

The Xyelidae hold status as the most primitive family, not only of the sawflies, but of all Hymenoptera. The xyelids are usually associated with a primitive plant group, coniferous trees (Ross 1932, Blank and Kramp 2017). The Macroxyelinae subfamily, however, is associated with angiosperms, and is likely the most primitive group of extant sawflies in the world (Smith and Schiff 1998).

Megaxyela adults are large, 8–15 mm in length, with distinctively long legs and orange/red coloration. Despite these easily noticeable characters, they are rarely observed (Smith and Schiff 1998, Blank et al. 2017)

Diversity

There are 13 described extant species worldwide. Seven occur in North America (Taeger et al. 2010, Blank et al. 2017).

A key to Nearctic species of Megaxyela is included in Smith and Schiff 1998.

Diagnostic characteristics

May be confused with

Xyelidae can be distinguished from other families by the long ovipositor and the characteristic elongate third antennal segment wider than the remaining flagellum. Megaxyela can be distinguished from Xyela and Pleroneura by the large size and from Xyelecia by the location of the Sc2/R vein junction. It can be distinguished from Macroxyela by the shape of the clypeus and the carina around the eye (Goulet 1992, Blank et al. 2017).

Exotic pest species of concern

none

Host associations

Larvae are external leaf feeders recorded on species of Juglandaceae, including Carya illinoinensis (hardy pecan), other Carya sp. (hickory), Juglans cinerea (butternut), and other Juglans sp. (walnut) (Smith and Schiff 1998, Blank et al. 2017).

Life history

The female positions herself on the leaf with her abdomen at the apex, head towards the base. She deposits one egg on the upper surface of the apex of the leaf, then slowly folds the leaf upwards, longitudinally along the midrib, sealing it with an excreted glue-like substance (Smith and Schiff 1998). Larvae are large, 22–28 mm in length at maturity, cylindrical, with brown head capsule and spiracles, as well as long, 6-segmented antennae (Smith 1967b, BugGuide 2019). Typically, the larvae are situated wrapped around the base of a leaf. As the larvae mature, they feed on the young leaves of the tree. Around June, larvae will fall to the ground and build a cocoon to pupate (Smith 1967b, Smith and Schiff 1998).

Adults fly during April and May. Megaxyela are univoltine (Smith and Schiff 1998).

Distribution

World: Megaxyela is recorded in North America and in East Asia, specifically in China, Korea, Russia, and Japan (Taeger et al. 2010, Blank et al. 2017).

North America: In North America, the range of Megaxyela is restricted to the eastern United States, from the Midwest east to the mid-Atlantic region, and Ontario, Canada (Blank et al. 2017).

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

Details about data used for maps can be found here.

Megaxyela major female lateral habitus; photo by J. Orr, WSDA

Megaxyela major female lateral habitus; photo by J. Orr, WSDA

Megaxyela major female dorsal habitus; photo by J. Orr, WSDA

Megaxyela major female dorsal habitus; photo by J. Orr, WSDA

Megaxyela major female face; photo by Q. Baine, WSDA

Megaxyela major female face; photo by Q. Baine, WSDA

Megaxyela major fore wing; photo by Q. Baine, WSDA

Megaxyela major fore wing; photo by Q. Baine, WSDA

Megaxyela major female antenna; photo by Q. Baine, WSDA

Megaxyela major female antenna; photo by Q. Baine, WSDA

Megaxyela major female clypeus; photo by Q. Baine, WSDA

Megaxyela major female clypeus; photo by Q. Baine, WSDA