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, coniferousconiferous:
describing a conifer
trees (Ross 1932, Blank and Kramp 2017Blank and Kramp 2017:
Blank SM and Kramp K. 2017. Xyela davidsmithi (Hymenoptera, Xyelidae), a new pine catkin sawfly with an unusual host association from the Sierra Nevada. Proceedings of the Entomological Society of Washington 119 (Special Issue): 703-717.). The Macroxyelinae subfamily, however, is associated with angiosperms, and is likely the most primitive group of extantextant:
in existence; opposite of extinct
sawflies in the world (Smith and Schiff 1998Smith and Schiff 1998:
Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657.).

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 1998Smith and Schiff 1998:
Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657., Blank et al. 2017Blank et al. 2017:
Blank SM, Kramp K, Smith DR, Sundukov YN, Wei M, and Shinohara A. 2017. Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1-46.)

Diversity

There are 13 described extantextant:
in existence; opposite of extinct
species worldwide. Seven occur in North America (Taeger et al. 2010Taeger et al. 2010:
Taeger A, Blank SM, and Liston AD. 2010. World Catalog of Symphyta (Hymenoptera). Zootaxa 2580: 1-1064., Blank et al. 2017Blank et al. 2017:
Blank SM, Kramp K, Smith DR, Sundukov YN, Wei M, and Shinohara A. 2017. Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1-46.).

A key to NearcticNearctic:
describing the region of the Northern Hemisphere that includes North America south through northern Mexico
species of Megaxyela is included in Smith and Schiff 1998Smith and Schiff 1998:
Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657..

Diagnostic characteristics

• pronotum pronotum:
  the anterodorsal part of the thorax, often situated posterior to the head
  slightly constricted in the center, as seen from above (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• width of the clypeusclypeus:
  sclerotized area on the front of the head located between the antennal insertions and labrum
  as measured at the basebase:
  the beginning or most proximal area of any structure
  , less than 0.6 the distance between the eyes (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• third antennal segment elongate and wide, about three times as long as the remaining apicalapical:
  towards the apex; farthest away from the body
  segments combined (Ross 1932)
• 2 apicalapical:
  towards the apex; farthest away from the body
  tibial spurs on the fore legfore leg:
  the first and anterior-most leg of the body
  (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• 3–4 preapicalpreapical:
  close to, but anterior to, the apex
  tibial spurs on the mid legmid leg:
  the second and middle leg between the fore leg and hind leg
  (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• antenna antenna:
  the sensory organ emerging from the front of the head, usually between the compound eyes and above the clypeus; includes the flagellum, scape and pedicel
  with 8–9 segments: scapescape:
  the first antennal segment
  , pedicelpedicel:
  the second antennal segment, between the scape and flagellum
  , and 6–7 flagellomeres (Smith and Schiff 1998Smith and Schiff 1998:
  Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657.)
• junction of veins Sc2 and R of the fore wingfore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  located beyond the junction of veins R and Rs (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• apical apical:
  towards the apex; farthest away from the body
  margin of clypeusclypeus:
  sclerotized area on the front of the head located between the antennal insertions and labrum
  with a medial projection (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• tarsal claw tarsal claw:
  sharpened appendage emerging from the apex of the tarsus
  deeply notched (Ross 1932)
• fine carinacarina:
  a ridge or raised edge
  along inside edge of eye (Blank et al. 2017Blank et al. 2017:
  Blank SM, Kramp K, Smith DR, Sundukov YN, Wei M, and Shinohara A. 2017. Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1-46.)

May be confused with

Xyelidae can be distinguished from other families by the long ovipositorovipositor:
the female organ that deposits eggs and is used to drill into plant tissue, located at the apex of the abdomen, made up of the lance and lancet
and the characteristic elongate third antennal segment wider than the remaining flagellumflagellum:
the third section of the antennae that includes all the segments beyond the pedicel; segments of the flagellum are known as flagellomeres
. Megaxyela can be distinguished from Xyela and Pleroneura by the large size and from Xyelecia by the location of the Sc2/R veinvein:
a tube-like, often darkened, structure on the wings
junction. It can be distinguished from Macroxyela by the shape of the clypeusclypeus:
sclerotized area on the front of the head located between the antennal insertions and labrum
and the carinacarina:
a ridge or raised edge
around the eye (Goulet 1992Goulet 1992:
Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication., Blank et al. 2017Blank et al. 2017:
Blank SM, Kramp K, Smith DR, Sundukov YN, Wei M, and Shinohara A. 2017. Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1-46.).

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 1998Smith and Schiff 1998:
Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657., Blank et al. 2017Blank et al. 2017:
Blank SM, Kramp K, Smith DR, Sundukov YN, Wei M, and Shinohara A. 2017. Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1-46.).

Life history

The female positions herself on the leaf with her abdomenabdomen:
the third and last segment of an insect's body; in sawflies this is usually made up of 11 segments (segments 9 and 10 often fused)
at the apexapex:
the end or most distal area of any structure
, head towards the basebase:
the beginning or most proximal area of any structure
. She deposits one egg on the upper surface of the apexapex:
the end or most distal area of any structure
of the leaf, then slowly folds the leaf upwards, longitudinally along the midrib, sealing it with an excreted glue-like substance (Smith and Schiff 1998Smith and Schiff 1998:
Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657.). LarvaeLarva:
the immature stage of holometabolous insects
are large, 22–28 mm in length at maturity, cylindrical, with brown head capsule and spiracles, as well as long, 6-segmented antennaeantenna:
the sensory organ emerging from the front of the head, usually between the compound eyes and above the clypeus; includes the flagellum, scape and pedicel
(Smith 1967bSmith 1967b:
Smith DR. 1967b. A review of the larvae of Xyelidae, with notes on the family classification (Hymenoptera). Annals of the Entomological Society of America 60 (2): 376-384., BugGuide 2019BugGuide 2019:
BugGuide. Accessed January 2019. https://bugguide.net). Typically, the larvaelarva:
the immature stage of holometabolous insects
are situated wrapped around the basebase:
the beginning or most proximal area of any structure
of a leaf. As the larvaelarva:
the immature stage of holometabolous insects
mature, they feed on the young leaves of the tree. Around June, larvaelarva:
the immature stage of holometabolous insects
will fall to the ground and build a cocoon to pupate (Smith 1967bSmith 1967b:
Smith DR. 1967b. A review of the larvae of Xyelidae, with notes on the family classification (Hymenoptera). Annals of the Entomological Society of America 60 (2): 376-384., Smith and Schiff 1998Smith and Schiff 1998:
Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657.).

Adults fly during April and May. Megaxyela are univoltineunivoltine:
describing an insect with a life cycle of one generation per year
(Smith and Schiff 1998Smith and Schiff 1998:
Smith DR and Schiff NM. 1998. The genera Macroxyela Kirby and Megaxyela Ashmead (Hymenoptera: Xyelidae) in North America. Proceedings of the Entomological Society of Washington 100 (4): 636-657.).

Distribution

World: Megaxyela is recorded in North America and in East Asia, specifically in China, Korea, Russia, and Japan (Taeger et al. 2010Taeger et al. 2010:
Taeger A, Blank SM, and Liston AD. 2010. World Catalog of Symphyta (Hymenoptera). Zootaxa 2580: 1-1064., Blank et al. 2017Blank et al. 2017:
Blank SM, Kramp K, Smith DR, Sundukov YN, Wei M, and Shinohara A. 2017. Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1-46.).

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. 2017Blank et al. 2017:
Blank SM, Kramp K, Smith DR, Sundukov YN, Wei M, and Shinohara A. 2017. Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1-46.).

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

Details about data used for maps can be found here.