Xyelidae Newman, 1834

Zheng, Yan, Hu, Haiyan, Chen, Dong, Chen, Jun, Zhang, Haichun & Rasnitsyn, Alexandr P., 2021, New fossil records of Xyelidae (Hymenoptera) from the Middle Jurassic of Inner Mongolia, China, European Journal of Taxonomy 733 (733), pp. 146-159 : 148-149

Family Xyelidae Newman, 1834

Remarks

The system of Xyelidae considering its present and past diversity was developed a half century ago ( Rasnitsyn 1966, 1969) and badly needs reconsideration now because the description of numerous new genera has made the diagnostic of tribes and subfamilies rather tricky and results in many mistakes. However this is a subject of a special work which is hardly possible to perform in the near future. In the meantime, to help current researches in the field of past diversity of the family, we have constructed an updated, although preliminary, key to the identification of the subfamilies and tribes of Xyelidae particularly addressed to fossil material.

Key to subfamilies and tribes of Xyelidae

1. Along R, cell 2r longer than, or as long as, or very rarely slightly shorter than, 1r. Triassic ............ 2

– Along R, cell 2r shorter than or, very rarely, as long as 1r. J-R (Jurassic through Recent)............... 3

2. Rs two-branched (cell 4r present)...................................................... Archexyelinae Rasnitsyn, 1964

– Rs simple (no 4r cell)........................................................................... Madygellinae Rasnitsyn, 1969

3. Costal space apical with no sclerotisation connecting C with R. Pterostigma not sclerotised (dark) except sometimes basally. Ovipositor long, extending behind abdomen, never very wide. Xyelinae ........................................................................................................................................................... 4

– Costal space apical with vertical sclerotisation between C with R delimited from pterostigma with costal break (membranose slit permitting pterostigma with distal wing to turn up and down at flight), or that area widely desclerotised, expanding to both end of costal space and base of pterostigma (as in Ceroxyelini ). Pterostigma sclerotised (dark) basally or throughout, sometimes except centrally. Ovipositor not narrow, extending far behind abdomen only when very wide. Macroxyelinae ......... 5

4. 1-Rs longer than 1-M, 1m-cu longer than 0.6× 3-Cu. J-R.............................. Xyelini Newman, 1834

– 1-Rs shorter than 1-M, 1m-cu at most 0.6× as long as 3-Cu. Jurassic and Early Cretaceous ............. .............................................................................................................. Liadoxyelini Rasnitsyn, 1966

5. Sc hind branch entering R distal of Rs base ...................................................................................... 6

– Sc hind branch entering R basal or at Rs base................................................................................... 7

6. 1-Rs shorter than 1-M. Area around costal break widely desclerotised. 1 st flagellomere much shorter than posterior flagellomeres together. Early Cretaceous ........................ Ceroxyelini Rasnitsyn, 1969

– 1-Rs not distinctly shorter than 1-M. Area around costal break narrowly or not at all desclerotised. 1 st flagellomere not shorter than posterior flagellomeres together. J-R ............................................... .............................................................................................................. Macroxyelini Ashmead, 1898

7. 1-Rs half as long as 1-M or shorter. Pterostigma sclerotised throughout or except centrally, usually with distinct desclerotisation around costal break. J-R ................................ Xyeleciini Benson, 1945

– 1-Rs distinctly longer than half 1-M. Pterostigma rarely with distinct desclerotisation around costal break. Jurassic and Early Cretaceous................................................................................................. 8

8. Pterostigma sclerotised basally........................................................... Angaridyelini Rasnitsyn, 1966

– Pterostigma sclerotised throughout (sometimes except centrally) .... Gigantoxyelini Rasnitsyn, 1969