Proisotoma, Borner, 1901

Potapov, Mikhail, Babenko, Anatoly & Fjellberg, Arne, 2006, Taxonomy of the Proisotoma complex. Redefinition of genera and description of new species of Scutisotoma and Weberacantha (Collembola, Isotomidae), Zootaxa 1382 (1), pp. 1-74 : 67-68

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 ). Only 1 prelabral chaeta present. Maxillary outer lobe with 1 sublobal hair ( Fig. 179 ). Th.III–Abd.I lacking sensilla ( Fig. 186 ) ........................................................................................................ 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 ) 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 ). Maxillary outer lobe with 4 sublobal hairs ................................................... 5

4 Sensilla on Abd.I–III in mid-tergal position ( Fig. 6 ). 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 ). 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 ). 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 ) ................ 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 ) .. 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 ). Labial papilla E with 5 guards (e 4 and e 7 absent) ( Fig. 16 ). 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 ). Labial papilla E with 6 guards (only e 7 absent) ( Fig. 17 ). Ant.3 with bms present (Fig. 25) .............................................. Scutisotoma Bagnall, 1949 (partim)

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

- The number of macrosensilla on Th.II–Abd.V is different. Sensilla on Abd.III set closer together ( Figs. 7–9 ). 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 , 158 ). PAO long and narrow ( Fig. 153 ) ................................................................................... Weberacantha Christiansen, 1951

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

Figures

FIGURES 177–185. Strenzketoma buddenbrocki. 177, furca, posterior view; 178, dens, anterior view; 179, head; 180, group of lateroventral sensilla (s) of Ant.1; 181, labial palp (A–E: papillae, note the small A and C, h: hypostomal projection); 182–185, tip of leg 2 (182–183) and leg 3 (184–185) (183 and 185 schematic).

FIGURES 186–187. Strenzketoma buddenbrocki. 186, chaetotaxy of Th.II–Abd.II; 187, general distribution of macrochaetae, sensilla and microsensilla on body.

FIGURES 12–17. Morphological characters of the Proisotoma-complex. 12–14, inner side of Ti. 2 in Proisotoma minuta (12) and Ballistura schoetti (13–14) (tibiotarsal chaetae B4, B5, and B4/5); 15–17, labial palp in Scutisotoma kolymica sp.n. (15), P. clavipila (16), and S. tianshanica (17) (papilla E, and guard e7 encircled).

FIGURES 6–11. Sensillary patterns in taxa with midtergal position of sensilla. 6, 10, general distribution of sensilla (s) and microsensilla (ms) in Scutisotoma muriphila (6) and “Proisotoma” ripicola (10); 7–9, 11, s and ms position on Abd.III in S. muriphila (7), S. armeriae (8), Scutisotoma sp. (U.S.A.) (9), and “Proisotoma” ripicola (11).

FIGURES 1–5. Sensillary patterns in taxa with posterior position of sensilla. 1, 3, 4, general distribution of sensilla (s) and microsensilla (ms) in Proisotoma minuta (1), Ballistura schoetti (3), and Subisotoma sp.1 aff. pusilla (Russia, Kaluga) (4); 2, 5, s and ms position on Abd.III in Proisotoma clavipila (2) and Subisotoma sp.2. aff. pusilla (Russia, Kunashir Isl.) (5).

FIGURES 156–168. Weberacantha echinodermata sp.n. 156, furca posterior; 157–158, dens, anterior (157) and lateral (158); 159, PAO and ocelli; 160, VT; 161, chaetotaxy of Abd.V (s: sensilla, connected); 162, microsensillum; 163, sensillum; 164, macrochaetae on Abd.IV; 165–167, Abd.V, spine-like macrochaetae (165), thick microchaeta (166) and sensillum (167); 168, general distribution of macrochaetae, sensilla and microsensilla on body.

FIGURES 151–155. Weberacantha octa. 151, general distribution of macrochaetae, sensilla and microsensilla on body; 152, dens, lateral view; 153, PAO and ocelli; 154, chaetotaxy of Abd.V (s: sensilla, connected); 155, claw on leg 3.