treatment provided by
Genus PHTHIRACARUS Perty
Definition: Weak to heavily sclerotized Phthiracaridae ranging in length from about 350- 1300 µm (lateral measurement taken in closed position). The integument of the dorsal and ventral shields, infracapitulum and chelicerae is densely punctate while that of the appendages is smooth. The interlamellar and lamellar setae are procumbent and the aspis without a median keel. The notogaster bears 15 pairs of fine and generally smooth setae. Fissures ip and ips may be present or absent. The notogaster bears neither a cowl nor a carina. Two pairs of anal setae are located on the paraxial margins of the anal plates and three pairs of adanals submarginally (the exception being P. anonymum with three pairs of setae located marginally). All are usually more or less equal in length although the two posterior pairs of adanal setae may be vestigial. The genital setae are arranged in a pattern of 5+4 along the paraxial margins of the genital plates. On leg IV the tibial solenidion is coupled.
Key to adults of the British species of the genus Phthiracarus
Only two species can be recognized on the basis of a Single character. In P. anonymum seta ad3 is located marginally (submarginally in all other species) while P. laevigatus appears to differ from all the other members of this genus in that the notogaster is strongly arched at the level of seta c1.
It has been concluded from an investigation of the external morphology of the British species that the number of setae on femur I (4 or 3) and genu IV (1 or 0), the shape of the sensillus, the presence or ab- sence of fissures ip and ips and the relative lengths and attitudes of the notogastral setae are the most useful characters for species differentiation. These are the main characters used in the following key.
1 Femur I with four setae (Fig. 4B); genu IV with a Single seta (Fig. 5C) .... 2
- Femur I with three setae (Fig. 14B); genu IV without setae ...... 9
2 Notogastral fissures ip and ips absent (Fig. 1A) ....... 3
- Notogastral fissures ip and ips present (Fig. 10D) ........ 6
3 Sensillus about 80 µm long, narrow and pointed distally (Pl. 4d); notogastral setae shorter than c1 - d1 .......... P. juvenalis sp. nov. (p. 342)
- Sensillus not of this form; notogastral setae equal to or greater than c, -d1 ... 4
4 Notogastral setae procurved (Fig. 7A); sensillus as in Pl. 3f .... P. clavatus sp. nov. (p. 338)
- Notogastral setae erect ............ 5
5 Large species, notogaster over 550 µm in length; seta d on femur I straight ... P. globus sp. nov. (p. 341)
- Smaller species, notogaster under 500 µm in length; seta d on femur I curved distally (Pl. 2d) ... P. affinis (Hull) (p. 335)
6 Notogaster sharply angled at the level of seta c1 when viewed laterally (Fig. 10D) ... P. laevigatus (C. L. Koch) (p. 344)
- Notogaster rounded anteriorly when viewed laterally (Fig. 1A). ..... 7
7 Sensillus 50-60 µm long, narrow and finely serrated (Fig. 12A); notogastral setae shorter than c1-d1 and procurved. ........ P. nitens (Nicolet) (p. 346)
- Sensillus not of this form; notogastral setae equal to or greater than c1-d1. ... 8
8 Notogastral setae procurved; on tarsus 1 seta coupled with solenidion omega2 much shorter than famulus ........... P. murphyi Harding (p. 346)
- Notogastral setae almost erect; on tarsus I seta coupled with solenidion omega2 almost as long as famulus .......... P. rectisetosus sp. nov. (p. 348)
9 Notogaster with vestigial f1 just dorsal to seta h1 (Fig. 6E); seta ad3 located on paraxial margin of anal plate (Pl. 3e); tarsus IV with eight setae (Fig. 6B) ... P. anonymum Grandjean (p. 336)
- Notogaster with vestigial f1 located on a level with or ventral to seta hx; seta ad3 located sub- marginally on anal plate (Fig. 2E); tarsus IV with nine setae (Fig. 14D). ... 10
10 Sensillus about 70 µm long ............ 11
- Sensillus 30-40 µm long ............ 12
11 Sensillus with membranous border (Fig. IIB).... P. membranifer sp. nov. (p. 344)
- Sensillus serrated distally (Fig. 13B) ..... P. serrulatus sp. nov. (p. 348)
12 Notogastral setae equal to c1-d1 and erect; tarsus II with 12 setae .... P. tardus Forsslund (p. 351)
- Notogastral setae greater than c1-d1 and slightly flexuose (Fig. 7F); tarsus II with 11 setae ....... P. flexisetosus sp. nov. (p. 340)
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.