(D. majuscula not included)

Males

1 Light medial band of tergum 10 complete (Figs 4, 33); apical half of paraproct caudal projections in profile appearing somewhat finger-like (Figs. 5, 6, 34, 35)........................................................................... 2

1’ Light medial band of tergum 10 incomplete, mesally interrupted by a darkly sclerotized transverse strip connecting the adjacent tergal halves (Figs. 48, 63); paraproct caudal projections in profile appearing as a right triangle, apical halves not appearing finger-like (Figs. 49, 50, 57, 59, 60, 64, 65, 72) ………….....................................................….. 3

2 Paraproct caudal projections in profile with apical frontodorsal margins not excavated, terminate in abruptly upturned, slightly bulbous tips that provide a boot-like appearance (Figs. 5, 6, 13, 24); tergum 9 with a noticeable mesal patch of sensilla basiconica (Fig. 4, 23); known distribution northeastern Nearctic realm, New Hampshire and possibly Quebec ………………… D. washingtoniana

2’ Paraproct caudal projections in profile resemble a Bowie knife blade in that the apical frontodorsal margins are noticeably ‘clipped out’ or excavated, terminate in broadly rounded tips that are not bulbous or so sharply upturned as to appear bootlike (Figs. 34, 35, 42, 45, 75); tergum 9 lacks a mesal patch of sensilla basiconica (Figs. 33, 74); known distribution Palearctic realm.................… D. nanseni

3 Paraproct caudal projections in dorsal or ventral view lack a bluntly pointed protuberance at midlength (Figs. 48, 49, 50, 51, 56); mesothoracic sternum with a complete sternacostal suture separating the basisternum from furcasternum (Fig. 47 ss); known distribution northern Holarctic ………………............................................. D. bicaudata

3’ Paraproct caudal projections in dorsal or ventral view each with a bluntly pointed protuberance at midlength (Figs. 63, 65, 66, 71); mesothoracic sternum with an incomplete sternacostal suture (Fig. 62); known distribution higher elevations of western North America………...……… D. knowltoni

Females

1 Spermatheca elongate, somewhat sausage-linkshaped (Figs. 10, 39 s), length greater than 2X width..………………………………………………………...2

1’ Spermatheca ovoid, somewhat egg-shaped (Figs. 54, 69 s), length approximately 1.3X width..…….…………………………………………………. 3

2 Known distribution eastern Nearctic realm, New Hampshire and possibly Quebec …………… …………………………..…………. D. washingtoniana

2’ Known distribution Palearctic realm. D. nanseni

3 Mesothoracic sternum with a complete sternacostal suture separating the basisternum from furcasternum (Fig. 47 ss); egg collar ring-shaped and stalked (Fig. 78) …………………… D. bicaudata

3’ Mesothoracic sternum with an incomplete sternacostal suture (Fig. 62); egg collar in dorsal view a Y-shaped triradiate ridge (Figs. 80, 81) ……………………………………….…... D. knowltoni