Phthiracarus serrulatus, Parry, B. W., 1979

Parry, B. W., 1979, A revision of the British species of the genus Phthiracarus Perty 1841 (Cryptostigmata: Euptyctima), Bull. British Mus. nat. Hist., Zool. ser. 35, pp. 323-363 : 348-350

Phthiracarus serrulatus sp. nov.

(Fig. 13A-C; Pl. 5b)

Adult (Pl. 5b): Small and weakly sclerotized. The aspis (Fig. 13C) ranges in length from 182-213 µm with a greatest width of 137-157 µm. All the dorsal setae are fine and short. Setae (il) are about 1-5 times the length of setae (la) and extend two-thirds of the distance il-ro. The rostrals which are inserted relatively far apart do not reach the anterior limit of the aspis. The sensillus (Fig. 13B) is long (70 µm), narrow and tapers to a point distally with three or four straight-edged teeth subterminally. The tracheoles are short and finger-like. The notogaster (Fig. 13A) ranges in length from 456 - 466 µm with a greatest depth of 324 - 334 µm. All the setae are relatively long (equal to the distance c1 - d1), fine and procurved. Seta c1 is inserted on the posterior collar margin and setae c2_3 submarginally. Vestigial f1 is located adjacent to seta h1 and towards the mid-dorsal line. The fissures ip and ips are absent. On each anal plate there are two setae in the anal series and one in the adanal series - all are moderately long and more or less equal in length. The chelicerae are approximately 120 µm long. The principal segment carries about 17 sharply pointed spines on the paraxial surface and about 16 conical spines antiaxially. The leg chaetotaxy is of the 'reduced type' with the setal formulae: I (1-3-2-5-15-1); II (1-3-2-3-11-1); III (2-2-1-2-10-1) and IV (2-1-0-2-9-1).

Types: Holotype, BMNH reg. no. 1976.2.18.12, and one paratype, 1976.2.18.13, from beech F, Wytham Woods Estate, Berkshire, 28.ix.70 (T. G. Wood). P. serrulatus is only known from the type locality.

Remarks: P. serrulatus shows an overall similarity to P. minimarginatus Woolley 1954, a species described from Colorado, USA. However, in comparison with serrulatus , the holotype of minimarginatus (dissected, partially cleared and mounted in Berlese's fluid) was found to possess shorter notogastral setae while vestigial f1 was located midway between setae h1 and ps1. Moreover, the sensillus of the American species was found to bear many more distal serrations rhan that of P. serrulatus . Both species are of a similar size (about 450 µm).