Phthiracarus globus, 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: 341-342

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Phthiracarus globus

sp. nov.

Phthiracarus globus  sp. nov.

(Figs 8; 9; Pl. 4a)

Adult (Pl. 4a): Large and moderately sclerotized. The aspis (Fig. 8C) ranges in length from 324 - 365 µm with a greatest width of 263 - 294 µm. All the dorsal setae are moderately long and fine. Setae (il) are about 1 -5 times the length of setae (la) and almost reach the level of the rostrals. The latter extend beyond the anterior margin of the aspis. The sensillus (Fig. 8B) is 50 - 60 µm long, lanceolate and serrated. It closely resembles that found in P. affinis  . The notogaster (Fig.8A), 578 - 852 µm long and with a greatest depth of 426 - 553 µm, is globular in lateral aspect. All the setae are long (more than the distance c1 - d1), fine and almost erect. Seta c3, is inserted on the posterior margin of the collar and setae c1_2 submarginally. Vestigial f1 is located adjacent to seta h1 and towards the mid-dorsal line. In one paratype f1 is located a short distance posterior to seta h1. The fissures ip and ips are absent. On each anal plate there are live long setae; an1-2 and ad3 being more or less equal in length and somewhat shorter than ad1-2 The chelicerae are approximately 208 µm long. The principal segment carries about 26 sharply pointed spines on the paraxial surface and about 24 conical spines antiaxially. The leg chaetotaxy is of the 'complete type' with the setal formulae: I (1-4-2-5-16-1); II (1-3-2-3-12-1); III (2-2-1-2-10-1) and IV (2-1-1-2-10-1). Seta d on femur I is long, straight and only weakly serrated (Fig. 9A). On tarsus II (Fig. 9B) seta ft" is hooked distally.

Types: Holotype, BMNH reg. no. 1976.2.18.3, from mosses and liverworts on rocks, Rydal Water, Westmorland, 29.i.54 (P. N. Lawrence). Two paratypes, 1976.2.18.4-5, from mosses, Long Compton Woods, Warwickshire, 15.viii.51 (P. N. Lawrence).

Distribution: P. globus  was also recorded in small numbers in the F and H layers under beech and oak at each of the study areas (see p. 324). Other material was examined from Wytham Woods Estate, Berkshire, 28.ix.70 (T. G. Wood) and from Woodwalton Fen, Huntingdonshire, 20.V.65 (P. N. Lawrence).

Remarks: Of the 'complete chaetotaxy' species examined, P. globus  is somewhat unusual in bearing f1 adjacent to h1, a feature generally associated with those species having the 'reduced chaetotaxy' combination.

P. globus  is similar to P. clavatus  . However, in contrast to the latter, the sensillus of P. globus  is lanceolate and the notogastral setae are distinctly procurved. Moreover, in P. globus  vestigial f1 is located much closer to the seta h1.