Key to the species of Protoribates of North America (adults)

1. Genital plates with 5 pairs of setae; sublamella vestigial; tutorium usually present as ridge or tectum; pteromorphs movable (Figs 4, 23 arrow)....................................................................... Protoribates ... (2)

- Genital plates with 4 pairs of setae; sublamella strongly developed, reaching lamellar seta; tutorium absent; pteromorphs immovable................................................................................. Lagenobates

2. Ventral keel of femur II smooth distally, without spur; posterior adanal setae ad1 – 2 both well developed, often subequal in length; tarsi either all monodactyl or all heterotridactyl; discidium various......................................... 3

- Ventral keel of femur II produced into a ventrally directed distal spur; posterior adanal setae ad1 very long and ad2 very short; tarsi I usually monodactyl and II–IV heterotridactyl or with variable number of claws; discidium subtriangular, cusp tapered, but not needle-like........................................................ Protoribates dentatus (Berlese, 1883)

3. Monodactyl (Figs 25–26, 29); sensillus (bo) relatively long (~1/3rd longer than lamella) and reflexed over notogaster (Fig 21); notogastral setae usually reduced to alveoli; acm complex on palp tarsus on distinct apophysis (Fig 20)................. 4

- Heterotridactyl (Figs 12–15); sensillus relatively short (~3/4ths length of lamella) and directed dorsally (Figs 3, 8–9); notogastral setae short, fine; acm complex on palp tarsus nearly sessile (Fig 11)................. Protoribates haughlandae sp. n.

4. Notogastral porose areas oval to subcircular (Figs 1, 23); sensillus acuminate, ciliate along margin (Fig 21).............. 5

- Porose area Aa (Fig 28) and A1 elongate to sinuate; sensillus truncate, without ciliate margin, ending in 2–3 short bristles........................................................................ Protoribates imperfectus (Banks, 1906)

5. Dorsophragmata normally produced, half length or less of mutual distance; lamellar setae long, extending beyond rostrum, interlamellar setae similar to lamellar setae; adanal setae ad 1 – 2 20–50 long, one or both usually visible in dorsal view; discidium with acuminate custodial tip; relatively large mites>465 long............................................... 6

- Dorsophragmata unusually long (~35–40), subequal to mutual distance (~30) (Fig 27); lamellar setae short, not extending beyond rostrum, interlamellar setae short, stout; adanal setae ad1 – 2 both short (~10), usually not visible in dorsal view; discidium large, rounded distally; smaller mites 320–440 long.......................... Protoribates capucinus Berlese, 1908

6. Sensillus sublanceolate or with fusiform head............................................................... 7

- Sensillus setiform, of even diameter to acuminate tip, without expanded head..... Protoribates lophotrichus (Berlese, 1904)

7. Tarsus I with 17 setae (l’’ and both pl absent) (Fig 25); notogastral seta lp (= f2) usually mesad porose area A1.................................................................................... Protoribates robustior (Jacot, 1937)

- Tarsus I with 20 setae (l’’ and both pl present) (Fig 29); notogastral seta lp (= f2) usually posteriad porose area A1................................................................................. Protoribates oblongus (Ewing, 1909)