Labiobaetis propinquus is the most common and widely dispersed species in Ontario. L. frondalis has been recorded from the Nottawasaga River system. The other two species have not yet been recorded from Ontario.
Species can be separated by the shape and distribution of submarginal setal on the labrum. The labrum must be removed from the specimen and mounted on a glass slide for observation under high power. L. frondalis has an irregular row of subapical setae composed of a variable number of distally expanded setae. L. propinquus has simple submarginal setae that occur in small clumps.
Print this card for a better view of the submarginal setae.