Identification determined April 30, 2003 by David R. Smith, Research Entomologist, USDA Systematic Entomology Laboratory.
Dolerus unicolor is becoming rare, being replaced by the closely related, more numerous (and presumably better adapted) D. nitens, according to Canada's Dept. of Natural Resources. My experience in the field bears this out - I encountered only two examples of D. unicolor this April, while D. nitens seems to be everywhere. Larvae of both species feed on various grasses.
More, larger images at Cirrus Digital Imaging