Proisotoma, Borner, 1901

Key to genera and “problematic” species of the Proisotoma complex

1 Ti.1–3 with at least 19-19-21 chaetae. More than 1 prelabral chaetae. Maxillary outer lobe with more than 1 sublobal hair. Macrosensilla present on Th.III–Abd.I............... 2

- Ti.1–3 with 18-18-19 chaetae ( Figs. 182–185 View FIGURES 177–185 ). Only 1 prelabral chaeta present. Maxillary outer lobe with 1 sublobal hair ( Fig. 179 View FIGURES 177–185 ). Th.III–Abd.I lacking sensilla ( Fig. 186 View FIGURES 186–187 )........................................................................................................ Strenzketoma gen. n.

2 Manubrium without anterior chaetae ............................................................................ 3

- Manubrium with anterior chaetae ................................................................................. 7

3 Unpaired medial chaeta on inner side of Ti.1–2 present ( Fig. 13 View FIGURES 12–17 ) or Ti.1–2 with only 19 chaetae. Maxillary outer lobe with 3 sublobal hairs................................................. 4

- Unpaired medial chaeta on inner side of Ti.1–2 absent. Ti.1–2 with 21 or more chaetae ( Fig. 12 View FIGURES 12–17 ). Maxillary outer lobe with 4 sublobal hairs ................................................... 5

4 Sensilla on Abd.I–III in mid-tergal position ( Fig. 6 View FIGURES 6–11 ). VT with 3+3 laterodistal chaetae. Dens with no more than 3 anterior and 6 posterior chaetae...... Folsomides Stach, 1922

- Sensilla on Abd.I–III in or near p-row of chaetae ( Fig. 3 View FIGURES 1–5 ). VT usually with more than 3+3 laterodistal chaetae. Dens usually with more than 3/6 chaetae................................................................................................................................... Ballistura Börner, 1906

5 Mucro large, at least half as long as dens (as on Fig. 158 View FIGURES 156–168 ). Abd.VI with a bundle of thick macrochaetae directed backwards................................ Narynia Martynova, 1967

- Mucro different, less than half as long as dens. Abd.VI with normal macrochaetae.... 6

6 Prelabral chaetae 4. Maxillary palp bifurcate. Microsensilla always 11/111. Sensilla on Abd.I–III in mid-tergal position ( Fig. 6 View FIGURES 6–11 )................ Scutisotoma Bagnall, 1949 ( partim)

- Prelabral chaetae 2. Maxillary palp simple. Microsensilla fewer than 11/111. Sensilla on Abd.I–III situated within or just in front of p-row ( Fig. 4 View FIGURES 1–5 ).. Subisotoma Stach, 1947

7 Prelabral chaetae 2 ........................................................................................................ 8

- Prelabral chaetae more than 2 ....................................................................................... 9

8 Antennae, head and lateral sides of tergites in males with many spine-like chaetae...... ..... “ Dimorphotoma ” porcellus Ellis, 1976 (The third species treated by Potapov (2001) as Dimorphotoma , viz. Proisotoma huadongensis Chen, 1985 from China is not included in the key as many important morphological features are unknown. Its generic position is also uncertain.)

- Spine-like chaetae absent in males. Posterior part of Abd.V with numerous integument notches...............................................“ Proisotoma ” multituberculata Martynova, 1971

9 Prelabral setae 3 .......................................................................................................... 10

- Prelabral setae 4 .......................................................................................................... 11

10 Macrosensilla on abdomen in p-row. Microsensilla on Th.II–Abd.III at most 10/000 ( Figs. 1, 2 View FIGURES 1–5 ). Labial papilla E with 5 guards (e 4 and e 7 absent) ( Fig. 16 View FIGURES 12–17 ). Maxillary outer lobe with simple palp. Ant.3 without bms (Fig. 24)............... Proisotoma Börner, 1901

- Macrosensilla on Abd.I–III well in front of p-row. Microsensilla on Th.II–Abd.III as 11/111 ( Fig. 6 View FIGURES 6–11 ). Labial papilla E with 6 guards (only e 7 absent) ( Fig. 17 View FIGURES 12–17 ). Ant.3 with bms present (Fig. 25).............................................. Scutisotoma Bagnall, 1949 ( partim)

11 Macrosensilla on Th.II–Abd.V always 33/22235 ( Fig. 10 View FIGURES 6–11 ). Lateral sensilla on Abd.III set far apart ( Fig. 11 View FIGURES 6–11 ). Ti.1–3 with 1-1-1 tenent chaetae. Furca long, mucro with 2 teeth .............................................................................“ Proisotoma ” tenella , ripicola View in CoL , biseta

- The number of macrosensilla on Th.II–Abd.V is different. Sensilla on Abd.III set closer together ( Figs. 7–9 View FIGURES 6–11 ). Ti.1–3 with 1-2-2 tenent chaetae, if differentiated. Furca and mucro variable ...................................................................................................... 12

12 Mucro large, 0.5–0.6 as long as dens ( Figs. 152 View FIGURES 151–155 , 158 View FIGURES 156–168 ). PAO long and narrow ( Fig. 153 View FIGURES 151–155 )................................................................................... Weberacantha Christiansen, 1951

- Mucro never more than 0.4 as long as dens. PAO wider..... Scutisotoma Bagnall, 1949