A new genus of Allantinae from India (Hymenoptera: Symphyta: Tenthredinidae)

Abstract

Introduction A new species described under a new genus, runs smoothly in Malaise’s (1963) key upto couplets 92 and 132 where these can be wrongly associated with genus Taxonus Hartig or Parasiobla Ashmead. If not studied in detail, this new species representing a new genus is likely to be mistakenly placed under Parasiobla, a genus that was erected by Ashmead (1898) with Taxonus rufocinctus Norton, its type species. Although Konow (1905) considerd Parasiobla a synonym of Taxonus, Malaise (1963) on the basis of the absence of closed middle cells in the hindwing, a character which is especially variable in rufocinctus, considered it a distinct genus. We agree with Smith's (1979) arguments that the criterion used by Malaise (1963) to split Taxonus Hartig into four genera: Taxonus, Strongylogastroidea, Hypotaxonus, and Parasiobla (=Polytaxonus) on the basis of variable, unstable and very weak characters such as the comparative length of hind basitarsus and presence or absence of closed middle cell in the hind wing are completely unreliable and thus unacceptable. Thus, we also consider all of them the synonyms of Taxonus Hartig. On the basis of some stable and reliable characters such as: extent and shape of clypeal incision; ratio of antennal segments 3 and 4; overall shape of antenna; presence or absence of postgenal as well as postorbital carinae; presence or absence of punctures on mesopleura; presence or absence of closed middle cell in hind wing; general direction and angle of cross vein, a new generic name Isotaxonus is proposed to treat the new species.