Morphological characteristics of water mite larvae of the genus Arrenurus Dugès, 1834, with notes on the phylogeny of the genus and an identification key Author Zawal, Andrzej text Zootaxa 2008 2008-05-07 1765 1 1 75 https://biotaxa.org/Zootaxa/article/view/zootaxa.1765.1.1 journal article 10.11646/zootaxa.1765.1.1 1175­5334 5123752 Arrenurus muelleri Koenike, 1901 (95) ( Fig. 31 ) Arrenurus lisii Maglio, 1908 Arrenurus muelleri spatiosus Viets, 1919 Material examined: 10 larvae deriving from 10 females . Larvae medium-sized: idiosoma 197–203 µm long. FIGURE 31. Arrenurus muelleri : A—ventral side, B—dorsal plate, C—excretory pore plate (scale bars: A, B—100 µm; C—20 µm). Dorsum : Dp relatively small (DpL: 188–195 µm ; DpW: 155–164 µm ), egg-shaped, widest at mid-length; posterior margin sharpened. Antero-lateral indents relatively small, strongly obtuse-angled, about 1/6 and 1/3 of plate’s length and width, respectively. DpW/Mp1-Mp1 4.7. Lp2, Mh1 smooth. Mp1-Mp1 short ( 32–35 µm ), shorter than Mp2-Mp2 ( 43–46 µm ); Mp1-Lp2 short ( 36–39 µm ). Venter : CpIIm short ( 23–24 µm ); CpI- IIm relatively long ( 37–39 µm ); CpIm long ( 62–69 µm ). CpI:CpII:CpIII ratio 2.9:1:1.6. All setae on Cp smooth. C1-CpIm ( 22–23 µm ) and C4-CpIIIm ( 23–25 µm ) almost equal length. C1-C2 short ( 35–36 µm ). Expp triangular, but elongated and thus sub-oval, longer than wide. Exp located below plate’s mid-point and below E2. Palps : PIII 1 bipectinate. Chelicerae : First segment elongated (73–76 ųm) and slightly bent, margins somewhat converging anteriorly. Legs : As long as body; LI< LII = LIII ( Fig. 4 ). ITi7 thick; ITi8 long; IFe3, IIFe3, IIIFe3 pectinate; IITi10, IIITi10 smooth, located in middle of tibia.