A REVISION OF THE NEARCTIC SPECIES OF THE TACHYDROMIINE FLY GENUSSTILPONLOEW (DIPTERA: EMPIDOIDEA)

Abstract

This revision recognizes 13 species ofStilponLoew in the Nearctic Region, including nine new species. A key is provided for the identification of adult specimens, all species are described, and their geographical distributions are mapped. Two informal species groups are recognized in the Nearctic Region, with the following included species: (1)S.graminumgroup —S.campestrisCumming sp.nov. (type-locality Assiniboia, Saskatchewan, Canada); (2)S.varipesgroup —S.chillcottiCumming sp.nov. (type-locality 10 km E Evergreen, Alabama, USA),S.ctenistesCumming sp.nov. (type-locality Salmon Creek, New York, USA),S.curvipesMelander,S.limitarisCumming sp.nov. (type-locality Sapelo Island,Georgia,USA),S.paucisetaMelander,S.pilomusCumming sp.nov. (type-locality Franconia, New Hampshire, USA),S.spinipesMelander,S.tribulosusCumming sp.nov. (type-locality Gatlinburg, Tennessee, USA),S.tyconyxCumming sp.nov. (type-locality Bedford, Massachusetts, USA),S.varipesLoew,S.vockerothiCumming sp.nov. (type-locality Ottawa, Ontario, Canada), andS.wirthiCumming sp.nov. (type-locality Dennisport, Massachusetts, USA). A world list of described species ofStilpon, including synonyms, is provided.Stilpon pectinigerMelander is a new junior synonym ofS.varipesLoew andS.demnatensisVaillant is indicated as a nomen nudum.Stilpon pleuriticusMelander, previously considered to belong withinStilpon, is excluded from the genus, andS.obscuripesAdams is transferred asCrossopalpus obscuripes(Adams) comb.nov. Lectotypes are designated forS.paucisetaMelander andS.pectinigerMelander. Homologies of previously confused structures of the male and female terminalia are summarized with reference to other Empidoidea. The monophyly ofStilponis justified, including discussion of the phylogenetic relationships of the genus to the remainder of the Tachydromiinae. All described species ofStilpon, including extralimital species, are assigned to one of three proposed informal species groups (S.divergens,S.graminum, orS.varipesgroup), and zoogeographic patterns are discussed.