394 A carology 



Composed of five segments, the palpi are simple. The maxillae have 

 two pairs of appendages: the exterior maxillary lobes are strongly 

 sclerotized, dentate at the tip, and two-segmented; the inner, thin max- 

 illary plates have three pairs of setae. The legs are five- or six-seg- 

 mented. Transverse sutures and transverse rows of setae may or may 

 not be present on the hysterosoma. The respiratory system consists of 

 stigmata on the exterior side of the base of the chelicerae and has 

 short tracheae (according to Tragardh). 



Although Grandjean 1932 di- 

 vided this group into three dis- 

 tinct families — the Palaeacaridae, 

 Acaronychidae, and Parhypoch- 

 thonidae — it is thought best for 

 the present to keep these mites in 

 one family — the Palaeacaridae — 

 with subfamily divisions. Tragardh 

 1932 erected a new suborder for 

 these, calling it Palaeacariformes; 

 Grandjean 1932 argued that these 

 mites were primitive oribatids and 



Figure 314 Acaronychus trdgardhi 

 Grandjean. Lateral view of female. 

 (After Grandjean 1932) 



Figure 315 Parhypochthonius aphidi- 

 niis Berlese. Dorsum of female. (After 

 Berlese 1904) 



did not constitute a separate group whereas Zakhvatkin 1945, 1946, 

 without further amplification, stated that his studies warranted the sub- 

 order rank given them by Tragardh. The present classification, that of 

 being the most primitive family of oribatids, is used more or less arbi- 

 trarily and, as in many cases, final decision will have to await further 

 work on the part of the specialists interested in these primitive forms. 



Key to the Palaeacaridae 



With six free leg segments 2 



With five free leg segments; hysterosoma with transverse sutures 

 and separated from propodosoma by suture Parhypochthoniinae 



