Key to species of Dufourea in eastern North America

[All species except D. marginata have been recorded from Michigan.]

1. Both sexes: Pubescence of body very dark (Fig. 2); compound eyes diverging below (Fig. 1). Male: Metasomal sternum six with strong ventrally-directed keel (Fig. 2) (specialist on Campanula; alpine/boreal distribution) ............. D. maura (Cresson)

—. Both sexes: Pubescence of body light in part (Fig. 3); compound eyes parallel or converging below. Male: Metasomal sternum six with apically-directed keel (Fig. 3) ........................................................................................................................... 2

2(1). Both sexes: Head longer than wide (Fig. 4) ............................................................. 3

—. Both sexes: Head wider than long (Fig. 5) ............................................................... 4

3(2). Female: Mouthparts (stipes, first labial palpomere) with abundant setae (Fig. 6); mesobasitarsus bowed posteriorly, width at midpoint distinctly greater than apex (Fig. 7). Male: Posterior margin of propodeal dorsum rugulose (Fig. 10); metatrochanter with ventral angle acute (Fig. 11); metasomal sternum six with oblique submedial swellings carinate (Fig. 12) (specialist on Pontederia) .............. .......................................................................................... D. novaeangliae (Robertson)

—. Female: Mouthparts bare (Fig. 8); mesobasitarsus parallel-sided, width at midpoint subqual to apex (Fig. 9). Male: Posterior margin of propodeal dorsum imbricate (Fig. 13); metatrochanter with ventral angle obtuse (Fig. 14); metasomal sternum six with oblique submedial swellings acarinate (Fig. 15) (specialist on Monarda) ................................................................................... D. monardae (Viereck)

4(2). Both sexes: Mesoscutum shiny, sparsely punctate across disc. Female: Clypeus with coarse punctures evenly distributed across surface (Fig. 16); mesotibial spur long, more than half as long as mesobasitarsus (Fig. 17). Male: Posterior margin of metasomal sternum five concave (Fig. 18); sternum six with low submedial ridge on each side of medial carina (specialist on Potentilla) ...................... .................................................................................................... D. harveyi (Cockerell)

—. Both sexes: Mesoscutum dull, contiguously punctate across disc. Female: Clypeus with fine punctures concentrated basally, clypeus impunctate apicomedially (Fig. 19); mesotibial spur short, less than half as long as mesobasitarsus (Fig. 20). Male: Posterior margin of metasomal sternum five straight (Fig. 21); sternum six without submedial ridge on each side of medial carina (specialist on Helianthus) ......................................................................... D. marginata (Cresson)