33^ ENTOMOLOGICAL NEWS [Nov., 'l8 



A New Tyroglyphid for Western Montana (Acar.).* 

 . By Ernest Carroll Faust, Ph.D., University of Illinois. 



(Plate XIX.) 



Among the parasites found by the writer on the Balsam- 

 root plant, Balsam orrhisa sagittata, in Western Montana, was 

 the interesting mite described in this paper. The creature 

 was found in Missoula, in June, 1916, gnawing and sucking the 

 juicy parts of the new leaves. Neither the rootstock nor the 

 underground stem was infected, nor were any other plants in 

 the vicinity attacked by this acarinid. 



The mite belongs to the Family Tyroglyphidae and to the 

 genus Rhisoglyphus. It is most nearly related to the species 

 R. Jiyaciuthi (Boisduval) and R. rhicnphagus Banks, both of 

 which have been reported for the same locality (Cooley 191^4, 

 Banks 1906). However, marked differences in several points 

 of structure in this mite justify the creation of a new species. 



Rhizoglyphus sagittatae nov. spec. (PI. XIX). 



Ovate oblong, creamy yellow in color, with a thin chitinous covering. 

 9 , 0.5 mm. long by 0.26 mm. wide ; S . 0.47 mm. long by 0.24 mm. wide. 

 The rostral platform stretches forward considerably anterior to the 

 main cephalic portion of the body. On the dorsum of this structure 

 is a single pair of prominent bristles. On each side just behind ap- 

 pendage IT is a single projecting bristle. In the posterior region of the 

 abdomen are three pairs of bristles, one ventral and two slightly dorsal. 

 The cephalothorax is separated from the abdomen dorsally by a 

 distinct sutural groove. 



One of the distinguishing features of the species, both male and 

 female, is the character of the appendage spines. They are flat plates, 

 broadly elliptic at the distal end, and fit deeply into the appendage at 

 the proximal end. The characteristic sickle-shaped graspins: spine at 

 the end of the tarsi in the female and at the end of tarsi I. II and IV 

 in the male is also plate-like and broadly lunar. 



Tarsi I and II of both sexes have an apical crest, consisting of one 

 lunar grasping spine and five elliptic spines. There is a single short 

 bristle arising from their midst. From the tibia of segments I and II 

 ajrise a large tactile bristle on the outside and an elliptic spine on the 

 inside. The genual bears a single inconspicuous bristle on its outer 

 margin. Tarsi I and II are appressed, so that they are broader than 

 long. Tarsi III and IV in the female and IV in the male are, on the 



* Contributions from the Zoological Laboratory of the University 



of Illinois under the Direction of Henrv B. Ward. 



