F. C.  Thompson, ?Keys to Nearctic Syrphidae (Diptera)?, p. 88, 1991.

A. V.  Barkalov and Mutin, V. A., ?Revision of hover-flies of the genus Blera Billberg, 1820 (Diptera, Syrphidae). 1?, Entomologicheskoe Obozrenie, vol. 70, pp. 204-213, 1991.