The Xyelidae are a comparatively species-poor family of sawflies, comprising about 80 Extant taxon species in five genera worldwide, and is the only family in the superfamily Xyeloidea.[ Taeger, A., Liston, A.D., Prous, M., Groll, E.K., Gehroldt, T. & Blank S.M. 2018: ECatSym – Electronic World Catalog of Symphyta (Insecta, Hymenoptera). Program version 5.0 (19 Dec 2018), data version 40 (23 Sep 2018). Senckenberg Deutsches Entomologisches Institut (SDEI), Müncheberg.]
The extant species occur in the Northern Hemisphere, especially in boreal ecosystem regions of the Holarctic, though there are a few Oriental species. Two genera and about 15 species occur in Europe.[Taeger, A., Blank, S.M. & Liston, A. D. 2006: European Sawflies (Hymenoptera: Symphyta) – A Species Checklist for the Countries. Pp. 399-504. In: Blank, S.M., Schmidt, S. & Taeger, A. (eds): Recent Sawfly Research: Synthesis and Prospects. Goecke & Evers, Keltern.][Blank, S.M. 2002: Biosystematics of the extant Xyelidae with particular emphasis on the Old World taxa (Insecta: Hymenoptera). Dissertation, Freie Universität Berlin.] Considering additional fossil records from Australia,[Riek, E. F. 1955: Fossil insects from the Triassic beds at Mt. Crosby, Queensland. Australian Journal of Zoology 3: 654-690.] South Africa[Schlüter, T. 2000: Moltenia rieki n. gen., n. sp. (Hymenoptera: Xyelidae?), a tentative sawfly from the Molteno Formation (Upper Triassic), South Africa. Paläontologische Zeitschrift 74(1/2): 75-78.] and Argentina,[Lara, M. B., Rasnitsyn, A. P. & Zavattieri, A. M. 2014: Potrerilloxyela menendezi gen. et sp. nov. from the Late Triassic of Argentina: The Oldest Representative of Xyelidae (Hymenoptera: Symphyta) for Americas. Paleontological Journal 48(2): 182-190.] the extant species display a relict distribution.
The species in the subfamily Xyelinae are associated with (esp. Pinus and Abies), where the feed on pollen or within buds. The larvae of the subfamily Macroxyelinae feed on the leaves of deciduous trees (various Juglandaceae and Ulmus).
The family is characterized by the appendages of the head, which are remarkable in that the antennae and palpi are nearly leg-like in structure, with a long basal segment followed by a series of tiny segments, as in the Arthropod leg.
Description
Imago (Adult)
Xyelidae are small Hymenoptera. Most species are 3 to 5 mm long, but species of
Macroxyela and
Megaxyela of East Asia and North America are larger, measuring 10 to 15 mm. The
imago display a number of ancestral characters of Hymenoptera, which may be absent in more derived lineages of Hymenoptera. Those include the absence of a wasp waist (thorax and abdomen abut without constriction), presence of
Cenchrus on the
metathorax to fix the wings at rest, presence of an antennal grooming apparatus on
tibia and first
tarsomere of the fore leg, and presence of a
molar tooth on the mandible. Most intriguing is the morphology of the antenna which bears a long and thick third article followed by a number of shorter and more slender
antennomeres. This so-called synantennomere 3
is the product from the
ontogenetic fusion of several antennal articles, and it is unique among the extant Hymenoptera species. In
Pleroneura,
Xyelecia and most species of
Xyela the maxillary palps are strongly enlarged and bear specialized
on the distal articles. The wing venation is the most complete among Hymenoptera: Only in Xyelidae the radial sector
Rs furcates into the veins
Rs1 and
Rs2, while in other Hymenoptera
Rs1 is absent. The females bear a more or less long
ovipositor, which in some species of
Xyela may be as long as the body. Morphology of the ovipositor and the ovipositor sheath are important characters for identification to species level. The penis valves of the males are densely setulous, which is a rare character state among the basal lineages of Hymenoptera. Females and males mate with the bodies directing in opposite direction. In Xyelinae the genital capsule of the males are revolved for 180° after disclosure from the pupal skin (
strophandry). Macroxyelinae are
orthandrous after emergence. They mate in the same position as Xyelinae, but the male genital capsule is rotated yet in course of mating (facultative strophandry).
[Schulmeister, S. 2001: Functional morphology of the male genitalia and copulation in lower Hymenoptera, with special emphasis on the Tenthredinoidea s. str. (Insecta, Hymenoptera, 'Symphyta'). Acta Zoologica 82: 331-349.]
Larva
Like in many other sawflies, the
of Xyelidae are superficially similar to
caterpillars of
Lepidoptera ("
eruciform" type of larvae). Larvae of species feeding inside plants are whitish, those of free-feeding species whitish green or yellow. Larvae of
Megaxyela bear a conspicuous pattern of black spots (see plate 21 figure 3 in
[Taeger, A.; Blank, S.M.; Liston, A.D. 2010: World Catalog of Symphyta (Hymenoptera). Zootaxa 2580: 1-1064.]) or they resemble bird droppings.
[Dyar, H.G. 1898: Description of an unusual saw-fly larva belonging to the Xyelinae. Psyche 8(265): 212-214.][Shinohara, A., Hara, H., Kramp, K., Blank, S. M. & Kameda, Y. 2017: Bird droppings on chestnut leaves or sawfly larvae: DNA barcodes verify the occurrence of the archaic Megaxyela togashii (Hymenoptera, Xyelidae) in Hokkaido, Japan. Zootaxa 4221(2): 220-232.] The roundish head capsule bears a larval eye (
stemmata) on each side, which is reduced in mining species, and short antennae comprising five articles. The
thorax bears short legs comprising three articles. Unlike the larvae of all other Hymenoptera and Lepidoptera which lack
on at least the first abdominal segment, larvae of Xyelidae have prolegs on all abdominal segments. In free feeding Xyelidae (
Macroxyela,
Megaxyela) the abdominal prolegs are conspicuous and consist of two articles, while in the mining species (
Pleroneura,
Xyela) they are reduced to inconspicuous transverse bulges.
Pupa
Unique among the Hymenoptera, the
pupa of Xyelidae are of the decticous and exarate types, in which the antennae, legs and mandibles are free and mobile.
This stage represents the already developed (
pharate) imago which is still enclosed by the pupal skin. At this stage, the wings are not expanded, and in females, the ovipositor and its sheath curve dorsally above the tip of the abdomen. The decticous pupae are capable of biting open the cocoon, digging to the surface of the ground, moving around on the surface, and drinking (figs 22-23 in
).
[Burdick, D.J. 1961: A taxonomic and biological study of the genus Xyela Dalman in North America. University of California Publications in Entomology 17(3): 285-355.] This pupal form is an ancestral character of
Holometabola. In other orders, it occurs in including
Neuropterida,
Mecoptera,
Trichoptera and in the basal lineages of
Lepidoptera.
[Weber, H. & Weidener, H. 1974: Grundriß der Insektenkunde. G. Fischer, Stuttgart, Studienausgabe, 640 pp.][Naumann, I. D. (ed.) 1991: The Insects of Australia. Melbourne Univ. Press, Carlton 1-2: 1-1137][Scoble, M.J. 1995: The Lepidoptera. Form, function and diversity. Nat. Hist. Mus., London and Oxford Univ. Press, Oxford et al., 404 pp. (reprint with corrections)] The Hymenoptera excluding Xyelidae are characterized by immobile adecticous pupae.
Ecology
The larvae of all Xyelidae are phytophagous and associated with trees. Larvae of the comparatively species-rich
Xyela live inside the growing staminate cones of
and feed on the sporophylls and the pollen. The North American
Xyela gallicaulis is exceptional in causing galls on fresh shoots of some pine species, inside which the larva feeds.
[Yates, H.O. III & Smith, D.R. 2009: History, Distribution, Damage, and Life Cycle of a Pine Shoot Gall Sawfly, Xyela gallicaulis (Hymenoptera: Xyelidae). Journal of Entomological Science 44: 276-283.] Larvae of
Pleroneura feed inside young shoots of
. Only the Japanese
Pleroneura piceae is associated with
spruce.
Larvae of Macroxyelinae are free feeders of deciduous tree species. The two North American species of
Macroxyela feed on
, the East Asian and North American species of
Megaxyela on
Juglandaceae like
Juglans,
hickory and
Pterocarya.
[Shinohara, A. 1992: The Sawfly Genus Megaxyela (Hymenoptera, Xyelidae) in East Asia. Japanese Journal of Entomology 60(4): 783-796.] For
Xyelecia nearctica an endophagous life style and an association with firs is supposed.
Many species of Xyelidae are host specific, with only a single larval host plant known. Monophagy is the prevailing life style in most species of Xyela.[Blank, S.M., Shinohara, A. & Byun, B.-K. 2005: The East Asian Xyela species (Hymenoptera: Xyelidae) associated with Japanese Red Pine ( Pinus densiflora; Pinaceae) and their distribution history. Insect Systematics & Evolution 36: 259-278.]
After completing feeding, Xyelidae larvae dig into the ground and form an earthen cell, where they usually spin a cocoon and develop into a pupa. Absence of a cocoon has been observed in Megaxyela togashii from Japan.[Saito, K., 1941: Ein (In Japanese.) Bull. agric. For. Coll. Suigen, (6): 1-235.]
Many species of Xyelidae facultatively diapause for several years. In Xyela alpigena and Xyela obscura a diapause of at least two years is obligate. This strategy might have evolved to ensure well developed cones are available for oviposition: the host plants Pinus cembra and Pinus mugo produce cones very irregularly in the subalpine zone of the European Alps.[Pschorn-Walcher, H. & Altenhofer, E. 2000: Langjährige Larvenaufsammlungen und Zuchten von Pflanzenwespen (Hymenoptera, Symphyta) in Mitteleuropa. Linzer biologische Beiträge 32(1): 273-327]
Adults of Xyela are pollen feeders of a variety of plants, which bear flowers with easily accessible pollen (e.g., Betula, Cercocarpus, Ostrya, Pinus, Purshia, Quercus, Salix).
Although they feed upon often economically important tree species, Xyelidae are usually of only small significance as pest organisms. Pleroneura piceae damages the growth of Sakhalin spruce, since the larvae destroy the young shoots.[Hara, H. 1996: Akaezomatsu no shin gaichu marunaginatahabachi. (In Japanese). Pleroneura Shinrin Hogo = 254: 25-26.] Larvae of Megaxyela major (and supposedly also of Megaxyela langstoni'') feed on leaves of pecan and are regarded as a pest of pecan plantations in the Southeastern USA.[Ree, B. 2012. Insects. Texas Pecan Pest Management Newsletter 12 (1): 1–3.][Ree, B. 2014. Sawfly. Texas Pecan Pest Management Newsletter 14 (2): 1–3.][Ree, B. 2016: Insects. Texas Pecan Pest Management Newsletter 16 (2): 1–3. PDF]
Systematics and taxonomy
Xyelidae represent the most basal lineage of Hymenoptera and very likely the
sister taxon of all other extant Hymenoptera. This assertion is supported by
phylogenetic analyses of both morphological characters and DNA sequences.
[Sharkey, M.J., Carpenter, J.M., Vilhelmsen, L., Heraty, J., Liljeblad, J., Dowling, A.P.G., Schulmeister, S., Murray, D., Deans, A.R., Ronquist, F., Krogmann, L., Wheeler, W.C. 2012: Phylogenetic relationships among superfamilies of Hymenoptera. Cladistics 28 (2012) 80-112. ] The great age of the family is supported by numerous fossil records. All Hymenoptera recorded from the
Triassic are classified as Xyelidae, while representatives of other hymenopterous families have been found no earlier than the
Jurassic. During the
Mesozoic and the
Tertiary period, the Xyelidae obviously were much more species-rich and more widely distributed than today. Thus, the comparatively few extant species can be regarded a relict group.
Extant taxa
The
Electronic World Catalog of Symphyta provides a complete account of the valid extant genera and species, their synonyms, the concerning references to original descriptions and distribution data on the level of countries and provinces.
-
Xyelinae
-
Pleroneura Konow, 1897: at least eight species in Eurasia
[Shinohara, A. 1995: The Sawfly Genus Pleroneura (Hymenoptera, Xyelidae) in East Asia. Japanese Journal of Entomology 63(4): 825-840][Blank, S.M. 2002: The Western Palaearctic Xyelidae (Hymenoptera). Pp. 197-233. In: Viitasaari, M. (ed.): Sawflies (Hymenoptera, Symphyta) I. A review of the suborder, the Western Palaearctic taxa of Xyeloidea and Pamphilioidea. Tremex, Helsinki. ( read online)][Shinohara, A. 2016: The sawfly genus Pleroneura (Hymenoptera, Xyelidae) of Japan: P. itoi n. sp. and a key to species. Zootaxa 4121(4): 495-500. ] and five in North America[Smith, D.R., Ohmart, C.P. & Dahlsten, D.L. 1977: The fir shoot-boring sawflies of the genus Pleroneura in North America (Hymenoptera: Xyelidae). Annals of the Entomological Society of America 70: 761-767.]
-
Xyela Brébisson, 1819 (synonyms: Pinicola Dalman, 1818 preoccupied,
[Vieillot, L.P. 1807–1809 Histoire naturelle des oiseaux de l'Amérique septentrionale, contenant un grand nombre d'espèces décrites ou figurées pour la première fois. Chez Desray, Paris, tome 1: 7 + i–iv + 1–90, tabs 1–57, tome 2: 4 + i–ii + 1–74, tabs 58–124. ] Xyelatana Benson, 1938
-
Xyela ( Pinicolites) Meunier, 1920: Xyela lata D.R. Smith, 1990 in western North America
[Smith, D.R. 1990: A new Xyela (Hymenoptera: Xyelidae) from western United States. Entomological News 101: 9-12.]
-
Xyela ( Xyela) Brébisson, 1819: 29 species in Eurasia
[Blank, S.M., Kramp, K. & Shinohara, A. 2017: Xyela fusca spec. nov. from Japan elucidates East Asian–North American relationships of Xyela (Hymenoptera, Xyelidae). Zootaxa 4303(1): 103–121. ] and 20 in North America,[Blank, S.M. & 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: 703- 717.] but many additional species have not yet been described.
-
Macroxyelinae
-
Macroxyela W.F. Kirby, 1882: Macroxyela aenea (Norton, 1872) und Macroxyela ferruginea (Say, 1824) in eastern and central North America
[Smith, D. R. & Schiff, N. M. 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 Ashmead, 1898: six species in eastern Eurasia,
[Blank, S.M., Kramp, K., Smith, D.R., Sundukov, Y.N., Wei, M. & Shinohara, A. 2017: Big and beautiful: the Megaxyela species (Hymenoptera, Xyelidae) of East Asia and North America. European Journal of Taxonomy 348: 1–46. ] seven species in North America.
-
Xyelecia Ross, 1932: two species, Xyelecia japonica Togashi, 1972 in Japan
[Togashi, I. 1972: Discovery of the genus Xylelecia Ross (Hymenoptera, Xyelidae) from Japan. Kontyû 40: 87-89.][Shinohara, A. 1998: Collection records of two rare xyelid sawflies (Hymenoptera, Symphyta) in Japan. Japanese Journal of Systematic Entomology 4: 389-390.] and Xyelecia nearctica in Western North America[Smith, D. R. 1964: Description of the Male of Xyelecia nearctica, with Comments on the Genus (Hymenoptera: Xyelidae). Pan-Pacific Entomologist 40(1): 54-56.][Smith, D.R. 1967: A review of the larvae of Xyelidae, with notes on the family classification (Hymenoptera). Annals of the Entomological Society of America 60: 376-384.]
The European species can be identified with help of „The Western Palaearctic Xyelidae“ of Blank (2002),[Blank, S.M., Shinohara, A. & Altenhofer, E. 2013: The Eurasian species of Xyela (Hymenoptera, Xyelidae): taxonomy, host plants and distribution. Zootaxa 3629: 1-106 PDF (Abstract).] The North American Macroxyelinae were revised by Smith & Schiff (1998),
Extinct taxa
The
Electronic World Catalog of Symphyta provides a complete account of the valid fossil genera and species, their synonyms and the concerning references to original descriptions.
Genus without classification into a subfamily of Xyelidae
†Archexyelinae
-
† Archexyela Riek, 1955, 2 fossil species
-
† Asioxyela Rasnitsyn, 1964, 4 fossil species
-
† Dinoxyela Rasnitsyn, 1969, 1 fossil species
-
† Euryxyela Rasnitsyn, 1964, 1 fossil species
-
† Ferganoxyela Rasnitsyn, 1969, 2 fossil species
-
† Leioxyela Rasnitsyn, 1969, 5 fossil species
-
† Lithoxyela Rasnitsyn, 1969, 1 fossil species
-
† Madygenius Rasnitsyn, 1969, 2 fossil species
-
† Moltenia Schlüter, 2000, 1 fossil species
-
† Oryctoxyela Rasnitsyn, 1969, 2 fossil species
-
† Triassoxyela Rasnitsyn, 1964, 3 fossil species
-
† Xaxexis Pagliano & Scaramozzino, 1990 =, 1 fossil species
-
† Xiphoxyela Rasnitsyn, 1969, 2 fossil species
-
† Xyelinus Rasnitsyn, 1964, 2 fossil species
Macroxyelinae
-
Genera without classification into a tribe of Macroxyelinae
-
†Angaridyelini
-
† Angaridyela Rasnitsyn, 1966, 8 fossil species
-
† Baissoxyela Rasnitsyn, 1969, 1 fossil species
-
† Ceratoxyela J. Zhang & X. Zhang, 2000, 1 fossil species
-
† Lethoxyela J. Zhang & X. Zhang, 2000, 2 fossil species
-
† Liaoxyela J. Zhang & X. Zhang, 2000, 1 fossil species
-
† Nigrimonticola Rasnitsyn, 1966, 1 fossil species
-
† Ophthalmoxyela Rasnitsyn, 1966, 1 fossil species
-
†Ceroxyelini
-
† Ceroxyela Rasnitsyn, 1966, 1 fossil species
-
† Isoxyela J. Zhang & X. Zhang, 2000, 1 fossil species
-
† Sinoxyela J. Zhang & X. Zhang, 2000, 1 fossil species
-
†Gigantoxyelini
-
† Abrotoxyela Gao, Ren & Shih, 2009, 2 fossil species
-
† Chaetoxyela Rasnitsyn, 1966, 1 fossil species
-
† Chionoxyela Rasnitsyn, 1993, 1 fossil species
-
† Gigantoxyela Rasnitsyn, 1966, 1 fossil species
-
† Heteroxyela J. Zhang & X. Zhang, 2000, 1 fossil species
-
† Platyxyela Wang, Shih & Ren, 2012, 1 fossil species
-
† Shartexyela Rasnitsyn, 2008, 1 fossil species
-
Macroxyelini
-
† Anthoxyela Rasnitsyn, 1977, 4 fossil species
-
Megaxyela Ashmead, 1898, 2 fossil species in addition to extant species
-
Xyeleciini
-
† Microxyelecia Rasnitsyn, 1969, 1 fossil species
-
† Uroxyela Rasnitsyn, 1966, 1 fossil species
-
Xyelecia Ross, 1932, 1 fossil species in addition to extant species
-
† Xyelites Rasnitsyn, 1966, 2 fossil species
†Madygellinae
Xyelinae
-
†Liadoxyelini
-
† Aequixyela Wang, Rasnitsyn & Ren, 2014, 1 fossil species
-
† Anomoxyela Rasnitsyn, 1966, 1 fossil species
-
† Cathayxyela Wang, Rasnitsyn & Ren, 2014, 1 fossil species
-
† Kirghizoxyela Rasnitsyn, 1966, 1 fossil species
-
† Liadoxyela Martynov, 1937, 3 fossil species
-
† Lydoxyela Rasnitsyn, 1966, 1 fossil species
-
† Orthoxyela Rasnitsyn, 1983, 1 fossil species
-
Xyelini
-
† Enneoxyela Rasnitsyn, 1966, 4 fossil species
-
† Eoxyela Rasnitsyn, 1965, 5 fossil species
-
† Spathoxyela Rasnitsyn, 1969, 2 fossil species
-
Xyela Dalman, 1819, 7 fossil species in addition to extant species, including Xyela ( Pinicolites) Meunier, 1920
-
† Xyelisca Rasnitsyn, 1969, 1 fossil species
-
† Yanoxyela Ren, Lu, Guo & Ji, 1995, 1 fossil species
