CHIRONOMIDAE (DIPTERA) OF THE COLORADO RIVER, GRAND-CANYON, ARIZONA, USA, I - SYSTEMATICS AND ECOLOGY

We describe the chironomid midge fauna of the Colorado River between G len Canyon Dam and Lake Mead, Arizona. This depauperate fauna, consist ing of 38 species, is dominated by euryecious Nearctic or Holarctic or thocladine taxa. In addition, a small Neotropical faunal component is represented by Polypedilum obelos Sublette & Sasa and Rheotanytarsus h amatus Sublette & Sasa. The following new synonyms are given: Protenth es riparius Malloch 1915 with Tanypus bellus Loew 1866 [=Procladius (P silotanypus) bellus (Loew)]; Cricotopus olivetus Boesel 1983 with Cric otopus (Cricotopus) annulator (Goetghebuer) 1927; Cricotopus edurus Su blette & Sublette 1971 with Orthocladius infuscatus Malloch 1915 [=Cri cotopus (Cricotopus) infus catus (Malloch)]; Cricotopus subfuscus Subl ette & Sublette 1971 with Orthocladius infuscatus Malloch 1915 [=Crico topus (Cricotopus) infuscatus (Malloch)]. The following new species ar e described: Cricotopus (Cricotopus) blinni Sublette, Cricotopus (Cric otopus) herrmanni Sublette, Metriocnemus stevensi Sublette, and Cladot anytarsus marki Sublette. We discuss the distribution and ecology of e ach chironomid species collected in this large, regulated, aridlands r iver.