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, 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.).

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 larvaelarva:
the immature stage of holometabolous insects
and adults, generally on the protein-rich pollen of male pine flowers (Smith 1990Smith 1990:
Smith DR. 1990. A new Xyela (Hymenoptera: Xyelidae) from western United States. Entomologist's News 101 (1): 9-12., Blank et al. 2013Blank et al. 2013:
Blank SM, Shinohara A, and Altenhofer E. 2013. The Eurasian species of Xyela (Hymenoptera, Xyelidae): taxonomy, host plants, and distribution. Zootaxa 3629 (1): 1-106. https://doi.org/10.11646/zootaxa.3629.1.1, 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.).

Diversity

There are 49 described extantextant:
in existence; opposite of extinct
species worldwide, restricted to the Northern Hemisphere. Twenty species 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 the North American species of Xyela is included in Burdick 1961Burdick 1961:
Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355..

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, about as long or slightly shorter than segments 4–12 combined (Burdick 1961Burdick 1961:
  Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355.)
• antennal segments 4–12 filiformfiliform:
  generally slender and of even diameter throughout
  ; narrower than 3 preceding segments (Burdick 1961Burdick 1961:
  Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355.)
• 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 12 segments: scapescape:
  the first antennal segment
  , pedicelpedicel:
  the second antennal segment, between the scape and flagellum
  , and 10 flagellomeres (Burdick 1961Burdick 1961:
  Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355.)
• ovipositor ovipositor:
  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
  long, measuring between slightly shorter than body length to longer than body length (Burdick 1961Burdick 1961:
  Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355.)
• vein vein:
  a tube-like, often darkened, structure on the wings
  Sc of fore wingfore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  very close, sometimes indistinguishable from veinvein:
  a tube-like, often darkened, structure on the wings
  R (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.)
• 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 basalbasal:
  towards the base; closest to the body
  to 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.)
• stigma stigma:
  a section of the fore wing at the apex of vein C that is sclerotized, rounded and often darkened
  of fore wingfore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  measuring twice as long as wide (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.)

May be confused with

Xyelidae can be distinguished from other sawfly 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 which is 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
. Xyela can be confused with other species in the genus. It can be distinguished by the number of antennal segments, the wing venationvenation:
the network of veins on a wing
, and small body size (Burdick 1961Burdick 1961:
Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355., 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.).

Exotic pest species of concern

None. While Xyela feeds on an economically significant plant family, the feeding behavior of the larvaelarva:
the immature stage of holometabolous insects
does not noticeably damage the tree (Burdick 1961Burdick 1961:
Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355.).

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 1978Smith 1978:
Smith DR. 1978. Suborder Symphyta (Xyelidae, Parachexyelidae, Parapamphiliidae, Xyelydidae, Karatavitidae, Gigasiricidae, Sepulcidae, Pseudosiricidae, Anaxyelidae, Siricidae, Xiphydriidae, Paroryssidae, Xyelotomidae, Blasticotomidae, Pergidae). Hymenopterorum Catalogus 14: 1-193., 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.). All Old-World species and the majority of North American species are monophagous (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.).

Adults feed on pollen from many sources, including Salix sp. (willow), Alnus sp. (alder), and Betula sp. (birch) (Smith 1990Smith 1990:
Smith DR. 1990. A new Xyela (Hymenoptera: Xyelidae) from western United States. Entomologist's News 101 (1): 9-12.).

Life history

The female uses the elongate 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
to deposit eggs into developing male cones. Emerged larvaelarva:
the immature stage of holometabolous insects
begin to feed on only pollen inside pollen sacs at the basebase:
the beginning or most proximal area of any structure
of the sporophylls, and consuming the sporophylls as the larvaelarva:
the immature stage of holometabolous insects
mature. Though they live inside the cone, they are not borers, and instead move among the sporophylls as the cone grows and opens. The larvaelarva:
the immature stage of holometabolous insects
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 1961Burdick 1961:
Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355., Yates and Smith 2009Smith 2009:
Smith DR. 2009. An obscure sawfly, Kerita fidala Ross (Hymenoptera: Tenthredinidae), new to Virginia, a leafminer of Virginia bluebell, Mertensia virginica (l.) Pers. Ex link (Boraginaceae). Banisteria 33: 53.).

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 larvalarva:
the immature stage of holometabolous insects
feeds on the stem tissue of the gall, then bores out of the gall to drop to the ground and pupate (Yates and Smith 2009Smith 2009:
Smith DR. 2009. An obscure sawfly, Kerita fidala Ross (Hymenoptera: Tenthredinidae), new to Virginia, a leafminer of Virginia bluebell, Mertensia virginica (l.) Pers. Ex link (Boraginaceae). Banisteria 33: 53.).

Xyela is most often univoltineunivoltine:
describing an insect with a life cycle of one generation per year
, with the exception of X. gallicaulis which has a life cycle of two years (Yates and Smith 2009Smith 2009:
Smith DR. 2009. An obscure sawfly, Kerita fidala Ross (Hymenoptera: Tenthredinidae), new to Virginia, a leafminer of Virginia bluebell, Mertensia virginica (l.) Pers. Ex link (Boraginaceae). Banisteria 33: 53.). Adults also feed on pollen during their flight period (Greenbaum 1974Greenbaum 1974:
Greenbaum HN. 1974. A new Xyela (Hymenoptera: Xyelidae) from Florida. The Florida Entomologist 57 (1): 104-106.).

Distribution

World: Xyela is widespread in Europe, Asia, and 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.). One species is endemicendemic:
both native and unique to a particular region
to the island of Taiwan (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: 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 1961Burdick 1961:
Burdick DJ. 1961. A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17 (3): 285-355.).

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

Details about data used for maps can be found here.