GENERIC LIMITS AND TAXONOMIC FEATURES OF SOME GENERA BELONGING TO THETRIBE OF CHRYSOGASTERINI (DIPTERA, SYRPHIDAE) .1. GENERIC DIAGNOSIS AND DESCRIPTION OF RIPOINNENSIA, GEN-NOV

A systematic review of the genera Lejogaster Rondani, Chrysogaster Mei gen and Orthonevra Macquart is presented, based on both larval and adu lt criteria. This study allows us to check the morphological features characteristic of each taxon as well as to define some new features an d leads to the following conclusions : - a) Lejogaster and Orthonevra are validly regarded as separate genera, rather than as subgenera of C hrysogaster, - b) Orthonevra, as recognised until now, comprises a pol yphyletic group of species in Europe : Orthonevra sensu stricto and Ri ponnensia, gen. nov. Riponnensia includes four species, R. splendens ( Meigen) [type species], R. daccordi (Claussen), R. insignis (Loew) and R. longicornis (Loew); - c) Chrysogaster sensu stricto comprises two distinct groups of species in Europe, that require recognition at gene ric level; the type species of the genus Chrysogaster, = C solstitiali s (Fal.), belongs to the first group, while Rondani's Melanogaster is available for the second group with M. nubilis Rondani as type species . The name nuda (Macquart) is established as the senior synonym of nub ilis Rondani, to replace lucida (Scopoli), which is shown (Maibach et al., in press) to have been wrongly applied. A dichotomous key, provid ing with the separation of the five genera, both at immature stages an d adults, completes this work.