Rhodacarus, Oudemans, 1902

Braga, Alice Freitas & Castilho, Raphael De Campos, 2024, New species of Binodacarus and Rhodacarus mites (Mesostigmata: Rhodacaridae) from Brazilian Cerrado biome, and a key to the world species of the genera, Zootaxa 5497 (1), pp. 70-82 : 79-80

Key to world species of Rhodacarus based on adult females

Twenty-nine species were mentioned by Castilho et al. (2012) in the genus Rhodacarus . Sufficient information is presently available in the literature to allow the recognition of the females of 27 species, including the new species described here. The following key was elaborated to help the separation of those species. Rhodacarus salarius Karg, 1993 , Rhodacarus strenzkei Willmann, 1957 and Rhodacarus willmanni Karg, 1993 , all from Germany, were not included because of the insufficient details provided in the original descriptions.

Despite Rhodacarus being the most numerous genus of Rhodacaridae , detailed revisions are necessary in most of the described species, in which the information in the original descriptions is insufficient to separate them. This situation causes taxonomic confusion about some groups of species of this genus, as already observed by Lee (1973), Bregetova & Shcherbak (1977), and Castilho et al. (2012).

In this key we draw attention to four groups of species where it is not possible to separate certain species. Detailed research will be necessary to resolve these taxonomic problems and we believe that the present study will provide a useful foundation for future taxonomic research.

1. Epistome with anterior section triangular................................. R. rhodacaropsis Ryke, 1962 ( South Africa)

- Epistome with an anteromedian extension, flanked by a pair of shorter anterolateral extensions........................ 2

2. With a pair of presternal platelets......................................... R. berrisfordi Loots, 1969 ( South Africa)

- Without presternal platelets............................................................................. 3

3. Podonotal shield with a line posterior of setae j 4, z 3 and s 2.................................................... 4

- Podonotal shield without a line posterior of setae j 4, z 3 and s 2................................................. 11

4. Ventrianal shield with six pairs of setae in addition to circumanal setae (Jv 1– Jv 3, Jv 5, Zv 1 and Zv 2)................................................................................ R. cuneatus Athias-Henriot, 1961 ( Algeria, France)

- Ventrianal shield with 4–5 pairs of setae in addition to circumanal setae.......................................... 5

5. Ventrianal shield with four pairs of setae (Jv 1– Jv 3 and Zv 2; Zv 1 on unsclerotised cuticle) in addition to circumanal setae... 6

- Ventrianal shield with five pairs of setae (Jv 1– Jv 3, Zv 1 and Zv 2) in addition to circumanal setae....................... 8

6. Seta Z 3 shorter than distance Z 3– Z 4....................................................................................... R. furmanae Shcherbak in Shcherbak & Furman, 1975 ( Georgia, Kyrgyzstan, Russia, Slovakia, Ukraine)

- Seta Z 3 as long as distance Z 3– Z 4........................................................................ 7

7. With rounded line posterior of setae j 4, z 3 and s 2; seta Jv 5 short, not reaching the posterior margin of the the ventrianal shield............................................ R. olgae Shcherbak in Shcherbak & Furman, 1975 ( Georgia, Ukraine)

- With V-shaped line posterior of setae j 4, z 3 and s 2; seta Jv 5 long, surpassing the posterior margin of the ventrianal shield...................................................................... R. longisetosus Shcherbak, 1980 ( Ukraine)

8. With a pair of elongate and a pair of rounded (with a pore-like structure) metapodal platelets, fused or not; seta r 4 on unsclerotised cuticle laterad podonotal shield.......................................................................... 9

- With a pair of elongate or rounded metapodal platelets; seta r 4 on podonotal shield................................ 10

9. With a pair of elongate and a pair of rounded (with a pore-like structure) metapodal platelets, fused.............. Group 1

- With a pair of elongate and a pair of rounded (with a pore-like structure) metapodal platelets, not fused........... Group 2

10. With a pair of elongate metapodal platelets; seta Z 3 shorter than distance Z 3– Z 4; seta Jv 5 short, not reaching the posterior margin of the the ventrianal shield................................... R. haarlovi Shcherbak, 1977 ( Latvia, Lithuania)

- With a pair of rounded metapodal platelets; seta Z 3 longer than distance Z 3– Z 4; seta Jv 5 long, surpassing the posterior margin of the ventrianal shield................... R. mandibularosimilis Shcherbak & Kadite, 1979 ( Lithuania, Poland, Ukraine)

11. Seta Zv 1 on unsclerotised cuticle anteriad ventrianal shield................................................... 12

- Seta Zv 1 on ventrianal shield........................................................................... 15

12. Seta Z 3 shorter than distance Z 3– Z 4; seta Jv 5 on ventrianal shield......................... R. emilianoi sp. nov. ( Brazil)

- Seta Z 3 longer than distance Z 3– Z 4; seta Jv 5 on unsclerotised cuticle laterad ventrianal shield....................... 13

13. Length of anterolateral extensions of epistome about one-seventh of the length of the anteromedian extension.............................................................................. R. gracilis Shcherbak, 1980 ( Turkmenistan)

- Length of anterolateral extensions of epistome about one third of the length of the anteromedian extension............. 14

14. Setae R 2– R 3 on opisthonotal shield; peritreme extending anteriorly to level of anterior margin of coxa III..................................................................................... R. marksae Domrow, 1957 ( Australia)

- Setae R 2– R 3 on unsclerotised cuticle laterad opisthonotal shield; peritreme extending anteriorly to level of posterior margin of coxa III.................................................................. R. fatrensis Kalúz, 1994 ( Slovakia)

15. Seta r 3 on unsclerotised cuticle laterad podonotal shield; setae R 2– R 5 on opisthonotal shield; seta Jv 5 on ventrianal shield.............................................................. R. matatlanticae Castilho & Moraes, 2010 ( Brazil)

- Seta r 3 on podonotal shield; setae R 2– R 5 on unsclerotised cuticle laterad opisthonotal shield; seta Jv 5 on unsclerotised cuticle laterad ventrianal shield............................................................................... 16

16. Seta r 4 on podonotal shield; seta Z 3 shorter than distance Z 3– Z 4.......................................... Group 3

- Seta r 4 on unsclerotised cuticle laterad podonotal shield; seta Z 3 longer than distance Z 3– Z 4................... Group 4