268 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 99 



extends beyond the palpal tarsus ; with none, one, or more plates on 

 the dorsum of the body; and with the palpi large and pincerlike. 



These mites as a whole are free-living predators, although some are 

 to be found in rabbit fur, squirrel fur, bird feathers, on cats, etc. 

 The free-living forms are found associated with infestations of acarid 

 mites (Acaridae), eriophyid mites (Eriophyidae), and scale insects 

 (Coccoidea), but as yet they do not appear to be of great importance 

 in controlling mites or insects. Carter et al. (Carter, H. F., Wedd, 

 G., and D'Abrera, V., Indian Med. Gaz., vol. 79, No. 4, pp. 163-1G8, 

 1944) report finding numerous mites in the sputum of patients suf- 

 fering from lung disorders, among these being a Cheyletus sp. Habits 

 of each species are listed in the main body of this report. Because 

 of their free-living habits the distribution of many of these mites is 

 world-wide. 



Since several of the genera are established on the number of dorsal 

 plates, confusion may arise because some of the nymphal forms have 

 two or more dorsal posterior plates instead of one. For example, the 

 n3^mph of Cheletofhyes haivaliensis, new species, possesses two dorsal 

 posterior plates, the nymph of Cheyletus cacahuamilpensis, new spe- 

 cies, possesses four dorsal posterior plates, and Oudemans (1921) in 

 discussing the generic status of GheJetomwms states that the nymjph 

 of €heyletia squamosa (Degeer) has two dorsal posterior plates. 

 Adults of CheJetoneJJa and Gheleto'psis have only the single dorsal 

 anterior plate; adults and nymphs of Cheletonmnus have a single 

 anterior plate and two posterior plates ; and adults of the other genera 

 have the usual anterior and posterior plates. 



The descriptions are based on material mounted on slides in balsam, 

 modified Berlese fluid, or polyvinyl alcohol (PVA) , and in most cases 

 the material has been flattened to some degree. The so-called balloon 

 setae of certain mites have been seen only on specimens which have 

 been mounted, and have been drawn as seen. The exact nature of these 

 setae on living mites is not known. Certain other types of setae pre- 

 sent the same problem. 



Only species in the National Museum Collection have been de- 

 scribed and figured. The other species are placed in the keys and are 

 listed in the text. 



Since Oudemans monographed the family in 1906, only a selected 

 bibliography of publications prior to that date is given, but references 

 to all important taxonomical publications since then are listed. Vitz- 

 thum (Die Tierwelt Mitteleuropas, vol. 3, No. 3, pp. 54-56, 1929) 

 gives keys to the European species, and Rodendorf (Wiss. Ber. Mos- 

 kauer Staats Univ. Zool., vol. 42, pp. 69-98, 1940) gives keys to the 

 Russian species. 



Types of new species, unless otherwise stated, are deposited in the 

 United States National Museum. 



