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 tetracyphus (O. F. Müller, 1776) ( Fig. 21 ) Material examined: 10 larvae deriving from 10 females . Larvae relatively large: idiosoma 214–260 µm long. Dorsum : Dp relatively large (DpL: 204–228 µm ; DpW: 152–176 µm ), egg-like and shield-shaped, widest in mid-length, with relatively large, obtuse-angled antero-lateral indents about 1/5 and 1/4 of dorsal plate’s length and width, respectively. DpW/Mp1-Mp1 3.1. Lp2, Mh1 pectinate, thicker than remaining setae. Mp1- Mp1 intermediate length ( 48–56 µm ), equal to Mp2-Mp2 ( 52–56 µm ); Mp1-Lp2 relatively short ( 34–43 µm ). Venter : Median margins of CpII very short ( 29–34 µm ), compared to those of CpIII ( 40–46 µm ) and CpI ( 70– 75 µm ). CpI:CpII:CpIII ratio 2.5:1:1.5. C2, C3, C4 bipectinate, C1 smooth. V 3 bipectinate; Lh2, Lh3 pectinate. C1-CpIm ( 20–23 µm ) more than 2/3 of C4-CpIIIm ( 34–38 µm ); C1-C2 intermediate ( 42–44 µm ). Expp pentagonal, clearly wider than long. Exp located slightly above plate’s mid-point, above E2. Palps : PIII 1 thick, bipectinate; PV6 short, thick. Chelicerae : First segment shaped like a curved cylinder, slightly tapered anteriorly ( 67–70 µm ). Legs : Somewhat shorter than body; LI< LII = LIII ( Fig. 4 ). ITi8 thin, long, pectinate; ITa13, IITa13, IITi10 long, pectinate. ITa12, IITa12, IIITa11, IIITa12, IIITa7, IIITa9, IIITa10 pectinate. IIITa14 only slightly closer to proximal end of tarsus than IIITa13 or at same level.