Blasticotomidae Thomson, 1871

Sun, Chenhui, Rasnitsyn, Alexandr P., Wedmann, Sonja, Zhuang, Jialiang, Shih, Chungkun, Ren, Dong & Gao, 2024, Revisions * new taxa * and venation transformations of the sawfly family Blasticotomidae sensu lato (Hymenoptera: ºenthredinoidea) highlight the evolution of the basal Hymenoptera, Zoological Journal of the Linnean Society 202 (1), pp. 1-19 : 2

Family Blasticotomidae Thomson, 1871 (= Xyelotomidae Rasnitsyn, 1968 )

Type genus: Blasticotoma Klug * 1834.

Diagnosis: Antenna with the first flagellomere several times longer and much thicker than following thread segments (reduced to one or no segments in Cenozoic Blasticotominae ). Wing venation characteristically tenthredinoid (with 2r-rs joining cell 3rm rather than 2rm) and complete (except for forewing with vein 2-RS lost in Cenozoic Blasticotominae ). Larva endophytic (feeding within fern stems)* with stemma touching antennal base dorsally* antenna setiform and consisting of six or seven segments. Legs setiform and six-segmented* with no prolegs present. Abdominal sterna dissected with transverse* oblique and longitudinal folds. Posterior terga sclerotized* concave and furnished with marginal processes.

Composition: The family is composed of four subfamilies: Blasticotominae Thomson * 1871* Dahurotomidae subfam. nov. * Pseudoxyelocerinae subfam. nov. * and Undatominae subfam. nov. * and the unplaced genus Zippelia Rasnitsyn & Müller * 2023* known only from a larva.

Remarks: The reasons to synonymize Xyelotomidae under Blasticotomidae are explained by Rasnitsyn and Müller (2023). In short* it is because of the high similarity of adult and particularly of larval morphology of the Mesozoic Xyelotomidae and Cenozoic Blasticotomidae . Under the resulting broader understanding of the family* it differs from other tenthredinoid families in having its flagellum differentiated into a long and thick basal segment and a thin segmented thread* except for some Cenozoic genera that have lost the thread-like antennal segments in Argidae and Zenargidae (for the latter* cf. Malagón-Aldana et al. 2021 a* b* Malagón-Aldana et al. 2022). However* Blasticotomidae differ from Argidae and Zenargidae in having a more complete wing venation and particularly in the forewing crossvein 2r-rs is always present (vs. lost in Argidae ).