Vol. Xxix | ENTOMOI.MC.ICAJ, NEWS 339 



not an internal borer, channeling subdermal passageways, as 

 R. hyacinthi is. Moreover, this species has always been found 

 as a parasite on an indigenous plant, common to the Western 

 uplands, while other rhizoglyphids described from this con- 

 tinent have been found on cultivated roots and bulbs, usually 

 imported stock. This fact argues favorably for the indi- 

 geneity of R. sagiltatae. 



Records of Rhizoglyphus species as human parasites are 

 not wanting. Dalgetty (1901) has shown that a dermatitis of 

 coolies in the Indian tea fields during the wet season is at- 

 tributable to a mite which has been designated as Rhizoglyphus 

 parasiticus. However, the presence of a sessile caroncle, the 

 lack of a distinct suture between cephalothorax and abdomen, 

 the absence of heteromorphic males, and the plumose struc- 

 ture of some of the spines, practically exclude this species 

 from the genus Rhisoglyphus. Similar records in the United 

 States (Pepper, Schnauss and Smith 1908) attribute cases of 

 intestinal dysentery to a mite "either identical with or more 

 probably a closely related species to Rhisoglyphus parasiticus 

 Dalgetty." While the latter acarinid more nearly conforms 

 to the tenus Rhizoglyphus, the data are too meagre to assign 

 it to a definite systematic position. On the whole, true parasit- 

 ism of Rhisoglyphus in man is questionable and not at all a 

 settled fact. 



SUMMARY. 



1. A new Tyroglyphid, Rhizoglyphus sagittatac, is de- 

 scribed from western Montana. It is closely related to R. 

 rhisophagus and R. hyacinthi, but is distinguished by the el- 

 liptic plate-like appendage spines and the paucity of bristles on 

 the appendages. 



2. The mite is superficially parasitic on the aerial portions 

 of an indigenous plant of the western range, Balsamorrliiza 

 sagittata. 



3. The study of this species tends to show a wide diversity 

 of the genus Rhizoglyphus. 



