No. 2303. RED SPIDERS OF AMERICA— McGREGOR. 661 



forelegs about four-fifths the length of body. Femur about two and 

 one-half times as long as thick, barely longer than the tarsus; tibia 

 and patella equal. Tip of tarsus bears a claw which is rather strongly 

 bent near base and only slightly arched for the rest of its length; it 

 appears to be uncleft for over half its length, and then divided into 

 six closely appressed spines. Tlie usual series of four tenent hairs 

 arise in pairs by the side of the claw base. The collar trachea, open- 

 ing medially in a pore, runs first downward and backward, then up- 

 ward and backward, and then upward and slightly forward. It is of 

 nearly even caliber throughout, but gradually enlarges a trifle toward 

 the hind end. Viewed as a whole it is very nearly sickle-shaped. 

 The penis (see pi. 79, fig. 1) is simple in structure, the shaft l)eing 

 very gradually attenuated to an extremely sharp point; it is very 

 slightly bent just distad to the middle, but is generally straight. 



Type.— Cat. No. 20169, U.S.N.M. 



From Oregon City, Oregon, from the leaves of white oak (Quercus 

 lobata), to which a noticeable rusty appearance is imparted through 

 the work of the species. 



TETRANYCHUS OREGONENSIS McGregor. 



Plate 79, fig. 2. 



Tetranychus oregonensis McGregor, 1917, Proc. L". S. Nat. Mus., vol. 51, no. 2167, 

 p. 585. 



Color, straw color or pale yellowish amber ; lateral spots lacking or 

 very inconspicuous. Eyes pale, a single one on either side near base 

 of subfrontal bristles. Legs and palpi paler than body. Dorsal 

 bristles 26, in four rows, plumose, pale, longest bristle (subfrontal) 

 equal to half the breadth of body. Body eUiptic-ovate, 0.304 mm. 

 long by 0.142 mm. wide; vertical thickness of body greatly reduced. 

 "Thumb" of palpus very short, nearly half again as wide as long, 

 bearing at its tip a fairly ample '^finger," whose base, however, is 

 slightly more than one-third the width of "thumb" at tip. On its 

 upper distal corner are two pseudo-fingers; on upper side hardly 

 midway to base is a very small "finger" or sensilla, and between this 

 and base are two short hairs ; a pair arises latero-ventrally from the 

 center of the "thumb." The claw on the penultimate joint reaches 

 to the dorsal "finger." The spur on the second joint of the male 

 palpus is rather long and tack-like. The legs are rather short, about 

 three-fourths the length of body. Femur hardly twice as long as 

 wide, equaling the tarsus; tibia one-fom'th longer than patella, which 

 barely surpasses the trochanter in length. Relative lengths of joints 

 as follows: Trochanter, 10; femur, 21; patella, 11; tibia, 14; tarsus, 

 21. Tip of tarsus bears a claw which is strongly bent below its 

 middle; the portion beyond this point is cleft into six nearly straight 



