NORTH AMERICAN APTERA. 285 



A Synopsis of the Harvest-Spiders (Plialaugiidee) 

 of South Dakota. 



BY CLARENCE M. WEED. 



I am indebted to Messrs. J. M. Aldrich and T. A. Williams for 

 an interesting collection of harvest-spiders from certain points in 

 South Dakota, chiefly Brookings and Custer. These specimens on 

 the whole are peculiar, because of the shortness of the legs and the 

 tendency to melanism. Possibly the former may be due to the fact 

 that in a prairie country long legs are less useful than in a wooded 

 region ; this seems especially likely, in view of the fact that, while 

 out-door forms have very short legs, P. cinereiim, which lives in sheds 

 and about houses, has legs of normal length. 



With the exception of the male Trachyrhinus favosus and Liohu- 

 num {f) calcar, the measurements given below are from South Dakota 

 specimens. 



Family PHALANGIID^. 



Teguments soft or coriaceous. Five or six ventral segments ; the 

 first very large and prolonged cephalad between the coxae. Anal 

 piece unique or accompanied by two small lateral pieces. Two eyes 

 situated upon a tubercle, always separated from the anterior border. 

 Two transverse strise on the cephalothorax back of the eye-eminence. 

 Lateral borders of cox^ free ; maxillary lobe of second pair always 

 visible. Palpi elongate ; tarsus longer than tibia, terminated by a 

 claw. Legs similar to each other; tarsi multi-articulate (Simon). 



Two subfamilies are represented in the collections at hand. They 

 may be distinguished as follows : 



Body very hard and greatly roughened by reticulations or tubercles. 



Mesosomatinse. 

 Body soft or subcoriaceous, not much roughened by reticulations or tubercles. 



Phalang-iinse . 



Subfamily Mesosomatin^. 



Body very hard, most of the dorsal segments being united in a 

 firm, dense plate ; much roughened by tubercles or reticulations. In 

 the males the posterior dorsal and the ventral abdominal segments 



TRANS. AM. ENT. SOC, XX. OCTOBER, 1893. 



