Key to adult females of Scaptococcus McKenzie

1(0) Circulus present; multilocular pores and modified oral collar tubular ducts present on both dorsum and venter; anal ring with cellular pores......................................................................................... 2

- Circulus absent; multilocular pores and modified oral collar tubular ducts restricted to venter; anal ring lacking cellular pores................................................................................. S. californicus McKenzie

2(1) Legs short and stout, with prothoracic tibia + tarsus shorter than femur; dorsal multilocular and quinquelocular pores and modified oral collar tubular ducts very few, scattered on posterior abdominal segments; body setae long and undulate (fig. 167 in McKenzie 1967); labium longer than clypeolabral shield...................................... S. milleri McKenzie

- Legs not short and stout, with prothoracic tibia + tarsus longer than femur; dorsal multilocular and quinquelocular pores and modified oral collar tubular ducts numerous, forming bands across thoracic and abdominal segments; body setae not long and undulate; labium as long as or shorter than clypeolabral shield (Fig. 5)............................. S. occultans sp. n.