SYSTEMATICS AND BIOLOGY OF ACENTRELLA-TURBIDA (MCDUNNOUGH) (EPHEMEROPTERA, BAETIDAE)

The larval stage of Acentrella turbida (McDunnough) is described for t he first time. Populations from British Columbia and Oregon are the ba sis of the description and also represent new geographic records for t he species. Acentrella carolina (Banks), the only other described spec ies of Acentrella lacking hindwings in North America, is shown to be a junior synonym of A. turbida. Keys are provided for distinguishing No rth American species of Acentrella in both the adult and larval stages . The European species A. sinaica Bogoescu is closely related to A. tu rbida, the two sharing nearly identical larval and adult morphology bu t differing mainly in the presence of absence of hindwings, respective ly. Abdominal coloration of male adults of A. turbida quickly fades in alcohol-preserved specimens. Notes on emergence times and habitat of A. turbida, based mainly from studies on the Atnarko River in British Columbia, are provided.