1. Tubercles De and Dl separated on the Abd. IV. De displaced to hind margin of the segment......................... 2
- Tubercles De and Dl fused into a single mass on the Abd. IV................................................. 13
2. Interocular area with 3 tubercles: 2 antennal and 1 frontal..................................................... 3
- Interocular area with 2 tubercles: composed of the fusion of each antennal with half of frontal....................... 12
3. Pigmented blue-black, not homogeneous, or pigment absent................................................... 4
- Body colorations blue-black, homogeneous................................................................ 7
4.- Yellow areas on the thoracic segments I and II, and abdominal I, II, III and IV. Mandible with three teeth...................................................................................... M. gilvipunctata (Uchida, 1938) (Japan)
- Dorsal ground whitish, with traces of pigment on dorsal tubercles. Mandible 5 or 7 teeth............................. 5
5. Prothorax with 8 tubercles.................................................... M. delicata Bernard, 2006 (USA)
- Prothorax with 6 tubercles as most Morulina spp............................................................. 6
6. Mandible with 5 teeth.................................................. M. pallidissima Cassagnau, 1997 (Japan)
- Mandible with 7 teeth.............................................. M. alia Christiansen & Bellinger, 1980 (USA)
7. Pectiniform mandible with 12–15 teeth, maxilla elongate....................................................................................... M. mackenziana Hammer, 1953 (Canada, Wrangel Island, Northern parts of Nearctic)
- Mandible with 5 ̶ 7 teeth, apical two more or less curved...................................................... 8
8. Maxilla with elongated capitulum, styliform, ocular tubercles with 2–3 setae...................................... 9
- Maxilla with short thick capitulum with 3 teeth, ocular tubercle with 5–6 setae.................................... 11
9. Ventral tube with 8–10 pairs of setae; mandible with 7 teeth................................ nucifera sp. nov. (China)
- Ventral tube with fewer than 8 setae; mandible with 5–6 teeth................................................. 10
10. Strong hypertrichosis, frontal tubercle with 5 setae. Macrosetae with globular or cylindrical apex. Di of Th. I with 4–7 setae........................................................................... M. orientis Tanaka, 1984 (Japan)
- Weak hypertrichosis, frontal tubercle with 2 setae. Macrosetae acuminate or tapering apex. Di of Th. I with 2 setae............................................................................. M. himalayana Cassagnau, 1977 (Nepal)
11. Strong hypertrichosis, Di of Th. I with 9–12 setae. Antennal tubercles with 9–12 setae. Mandible with 5 teeth.................................................................................. M. alata Yosii 1954 (Russia and Japan)
- Weak hypertrichosis, Di of Th. I with 3–7 setae. Antennal tubercles with 5–7 setae. Mandible with 6 teeth whose of apex out- ward–hooking................................... M. thulensis Hammer, 1953 (Nearctic & North–Eastern Palearctic)
12. Cephalic tubercles Di+De with 8–10 setae.............................. M. triverrucosa Tanaka 1978 (Japan, Korea)
- Cephalic tubercles Di+De with 6–7 setae; hypertrichosis usually less intense than in previous species (M. triverrucosa)................................................................ M. pawlowskii Deharveng & Weiner, 1984 (Korea)
13. Ocular tubercle with more than 3 setae................................................................... 14
- Ocular tubercle with 3 setae............................................................................ 16
14. Ocular tubercle with 4 setae................................................... M. callowayia Wray, 1953 (USA)
- Ocular tubercle with more than 4 setae................................................................... 15
15. Ocular tubercle with 5–6 setae. Mouthparts not elongated: maxilla with capitulum thick and short, apex with 3 teeth; mandible with 6 teeth.............................................. M. gigantea (Tullberg, 1877) (Siberia, Alaska, Sakhalin)
- Ocular tubercle with 6–7 setae. Mouthparts elongated: Maxilla with 4 reduced lamellae, mandible with 5 teeth............................................................. M. stevehopkini Palacios ̶Va rg a s & Si m ón ̶Benito, 2007 (USA)
16. Maxilla with a stout capitulum composed of 6 strong teeth and 2 slender lamellae.................................................................................................. M. crassa Chistiansen & Bellinger, 1980 (USA)
- Maxilla styliform, with 2–3 lamellae, one of them with (less than 6) or without teeth............................... 17
17. Mandible with 11–13 teeth.......................................... M. theeli Babenko & Fjellberg, 2001 (Siberia)
- Mandible with fewer than 8 teeth........................................................................ 18
18. Mandible with 7–8 teeth.............................................. M. verrucosa (Börner, 1903) (Carpathians)
- Mandible with 5 or 6 teeth............................................................................ 19
19. Mandible with 5 curved teeth. Ventral tube with 5–6 setae........................... M. australis Tanaka 1984 (Japan)
- Mandible with 6 teeth. Ventral tube with 8–12 setae....................... M. multatuberculata (Coleman, 1941) (USA)