Hydrachna
Creators: name: Smit, Harry
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Hydrachnidae
Hydrachna

description: Key for adults of the Australian Hydrachna species
1. Dorsum with large frontal plate(s) (Figs. 7A, 8A)........................................................... 2
- Dorsum with only very small sclerites (Fig. 3a)............................................................. 12
2. Dorsum with a pair of frontal sclerites (Fig. 7A)............................................................. 3
- Dorsum with one large frontal plate (Fig. 8A)............................................................... 5
3. Dorsal frontal sclerites relatively slender, curved, posteriorly not narrowed (Fig. 7A)............... H. longiscutata n. sp.
- Dorsal frontal sclerites relatively wide.................................................................... 4
4. Dorsal frontal plates very wide, pointed posteriorly (see Fig. 5 Smit 1992)......................... H. palustris female
- Dorsal frontal plates less wide, posteriorly narrowed (Fig. 1A)...................................... H. conjectoides
5. Dorsum with a simple large frontal plate, without lateral extensions, not surrounding the eyes........................ 6
- Dorsal frontal plate surrounding the eyes or extending laterally or to posterior idiosoma margin....................... 9
6. Posterior margin of frontal plate with a wide indentation (see Table I, fig. 4 Lundblad 1947).......... H. triscutatus female
- Posterior margin of frontal plate straight or only slightly concave................................................ 7
7. Dorsal frontal plate with 2–3 pairs of setae in posterior half (see Fig. 22 Cook 1967)............... H. mysorensis female
- Dorsal frontal plate with one pair of setae in posterior half.................................................... 8
8. Male genital field heart-shaped, longer than wide; fourth coxae of female posteromedially wide (Figs. 2C, E)..................................................................................................... H. cordata n. sp.
- Male genital field wider than long, bilobate; fourth coxae of female posteromedially narrow (Figs. 8C, E ................................................................................................. H. novaehollandica n. sp.
9. Dorsal frontal plate surrounding the eyes, with lateral extensions but not extending to posterior idiosoma margin (Fig. 1 Smit 1992; fig. 6 Cook 1986)..................................................Male: H. palustris, female: H. bilobata
- Dorsal plates either surrounding the eyes or eyes free, but frontal plate extending to posterior idiosoma margin......... 10
10. Besides the frontal plate also a lateral sclerite present (Fig. 2A Lundblad 1947)....................... H. triscutata male
- Only frontal plate present.............................................................................. 11
11. Frontal plate very large, extending onto lateral sides of idiosoma, genital field not bilobate (Fig. 26 Cook 1967)................................................................................................ H. mysorensis male
- Frontal plates only covering dorsum, genital field bilobate (Figs. 2, 7 Cook 1986)...................... H. bilobata male
12. Small frontal sclerites rod-shaped (Fig. 3A)................................................ H. curtiscutata n. sp.
- Small frontal sclerites not rod-shaped.................................................................... 13
13. Palp very stocky, L/H PIII <2.5......................................................................... 14
- Palp not very stocky, L/H PIII>2.6...................................................................... 15
14. Fourth coxal plates almost without posteromedial extensions, acetabula small and very numerous (Fig. 5A)..... H. hamata
- Fourth coxal with narrow posteromedial extensions, acetabula larger and less numerous (Fig. 1 Halík 1940). H. approximata
15. Palp very slender, L/H PIII> 4.0............................................................... H. tasmanica
- Palp less slender, L/H PIII <3.9....................................................................... 16
16. Males (genital field longer than wide).................................................................... 17
- Females (genital field wider than long)....................................................................19
17. Male genital field not intended anteriorly (Fig. 10B)....................................... H. queenslandica n. sp.
- Male genital field indented anteriorly..................................................................... 18
18. Male genital field deeply indented anteriorly, indentation reaching almost middle of genital field; capitulum elongated (Fig. 3D Lundblad 1947)............................................................................ H. australica
- Male genital field less indentated, capitulum not elongated............................................. H. linderi
19. Genital field deeply indented anteriorly, capitulum elongated (Fig. 3C Lundblad 1947).............. H. australica female
- Genital field only slightly indented anteriorly, capitulum not elongated (Fig. 5 D Lundblad 1947)..................... 20
20. PIII more than 280 µm long, genital field more than 400 µm wide.................................. H. linderi female
- PIII less than 200 µm long, genital field less than 300 µm wide........................ H. queenslandica n. sp. female
description: Published as part of Smit, Harry, 2014, Australian water mites of the genus Hydrachna Müller, with the description of five new species (Acari: Hydrachnidia: Hydrachnidae), pp. 170-186 in Zootaxa 3827 (2) on pages 185-186, DOI: 10.11646/zootaxa.3827.2.3, http://zenodo.org/record/225232