Atropacarus Ewing

[Genus Atropacarus Ewing]

Introduction

The genus Atropacarus (type, Hoplophora stricula C. L. Koch) was proposed by Ewing (1917) for monodactyl 'Hoplodermatinae' (= Euptyctima) with a sculptured integument but without a median aspal carina. Jacot later (1930) submerged the genus in Steganacarus, giving it subgeneric ranking with Tropacarus, while Grandjean (1934) regarded the presence of an additional pair of setae in the posterolateral region of the notogaster as sufficient reason for retaining Atropacarus as a separate genus. Although Atropacarus has remained monotypic, Sheals (1969), in the course of a numerical taxonomic study of certain Phthiracaroidea, recognized three further species which he considered might be classified in this genus. These were Steganacarus diaphanum Jacot and two undescribed Steganacarus species from Italy and Nepal; the latter is here regarded as a 'variant' of S. striculus and the former as Steganacarus clavigerus (Berlese). Together with striculus, these species formed a distinct component within Steganacarus in being relatively small (notogastral length 300-475 µm), possessing at least 16 pairs of notogastral setae and having a coupled solenidion on tibia IV (this solenidion is free throughout the rest of the genus). However, while size is usually given in modern descriptions, there is little information available on the chaetotactic pattern of the legs and notogaster, but it would seem that the combination of characters exhibited by the above species may be present in further described species of Steganacarus. Accordingly, a search was undertaken of all the available Steganacarus material which superficially resembled striculus - the results of a preliminary survey indicated that the genus Atropacarus * should be retained.

*Since this manuscript went to press a paper has been published by Aoki (25 March. 1980. Bull. Inst. Sci. Technol, Yokohama 6(2): 1-88.) in which he separates Atropacarus from Steganacarus to include the species A. phyllophorus. A. serratus and A. striculus. Therefore, in the present paper Atropacarus phyllophorus is not a new combination.

Genus ATROPACARUS Ewing

Atropacarus Ewing, 1917: 131; Balogh, 1972: 43.

Steganacarus: Jacot, 1930: 210 (in part).

Definition: Moderately sclerotized, rather elongate Phthiracaridae ranging in length from about 300-500 µm (lateral measurement of notogaster taken from the anterodorsal limit of the collar to a point just ventral to seta h1). The integument of the dorsal and ventral shields is usually strongly ornamented while that of the infracapitulum, chelicerae and appendages is densely punctate. The interlamellar and lamellar setae are short and procumbent and the aspis bears a median keel. Sensillus cranked near the base. The notogaster bears at least 16 pairs of setae. A notogastral cowl may be present or absent. Fissures ip and ips are absent. Four pairs of anal setae are located on the paraxial margins of the anal plates and a Single pair of adanals submarginally. There are at least seven pairs of genital setae along the paraxial margins of the genital plates. On tarsus I the posterior anterolateral seta is reduced and inserted adjacent to, or distally, in relation to the posterior fastigial seta. On leg IV the tibial solenidion is coupled.

Diagnosis: Atropacarus can be distinguished as a phthiracarid genus with the following combination of characters:

1 Notogaster with 16 or more pairs of setae.

2 Posterior anterolateral seta on tarsus I reduced.

3 Solenidion on tibia IV coupled with a reduced dorsal seta.

Key to species of the genus Atropacarus

1 Notogaster with 20 pairs of broad, serrated setae (Fig. 13); setae (il) and (la) more or less equal in length (Fig. 16); seta a" about half as long as famulus and closely associated with seta ft"(Fig. 19).............. A. clavigerus (Berlese) (p. 195)

- Notogaster with 16 pairs of setae (Fig. 4); setae (il) at least twice the length of (la) (Fig. 2); seta a" almost as long as famulus and located on a level with solenidion omega2 (Fig. 9).................... 2

2 Notogaster without a cowl (Fig. 4); setae stout and serrated distally (Fig. 33)........................ A. striculus (C. L. Koch) (p. 190)

- Notogaster with a well-developed cowl (Fig. 20); setae not of this form...................... 3

3 Notogastral setae spatulate and serrated (Fig. 20); integument reticulate...................... A. phyllophorus (Berlese) (p. 197)

- Notogastral setae stout and apparently smooth (Fig. 27); integument rugose...................... A. terrapene (Jacot) (p. 200)