584 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



An ample series of measurements of individuals of this species have 

 yielded the following averages : 



TETRANYCHUS MONTICOLUS, new species. 



Body of a rather uniform pale amber color. Eyes pale; one cornea 

 on each side close behind the subfrontal bristle, behind which are the 

 carrot-colored eye spots. Legs and palpi rather paler than body. 

 Dorsal bristles colorless, distinctly plumose, 26 in four rows, the long- 

 est about five-ninths the width of body. Body pyi-iform-elhptic, 

 usually widest between legs II and III. Mandibular plate nearly 

 three times as long as broad, narrowed considerably anteriorly to a 

 well-rounded, unemarginated tip. "Thumb" of palpus two-thirds 

 as long as broad, bearing on its truncate tip a subconieal "finger," 

 whose base is only two-fifths as wide as the tip of the "thumb." On 

 its upper distal corner are two pin-shaped pseudo-fingers, in length 

 somewhat exceeding the terminal "finger," on upper side, about a 

 third the distance to base, is a very small "finger;" and immediately 

 proximad to this is a short hair. Another similiar hair occurs on the 

 upper side just at base; a hair arises on the ventral aspect of the 

 "thumb." The claw of the penultimate jomt does not reach quite 

 to the dorsal "finger." The legs are short, not much over two-thirds 

 the length of body (exclusive of palpi). Femur a httle more than 

 twice as long as wide, not quite as long as tarsus; tibia a httle longer 

 than patella, which is five-sevenths again as long as the trochanter. 

 Relative length of joints is as follows: Coxa, 8; trochanter, 7; femur, 

 20; patella, 12; tibia, 14; tarsus, 22. Tip of tarsus bears a claw 

 which is bent near its middle and cleft into six slightly curved spurs. 

 The customary four capitate hairs arise, two on either side by base of 

 claw, tarsal claw of male differing from that of female in that its six 

 divisions are much shorter and more abruptly accuminate. The 

 coUar trachea is rather novel; it runs downward and backward from 

 the pore, then turns suddenly upward and backward to form an angle 

 of about 130°, and then the superior arm bends abruptly forward and 

 upward, paralleling the inferior arm. The superior arm is much 

 shorter and of somewhat smaller caliber than the inferior arm. The 

 penis is of unusual ty^e. The short inner lobe is rod-hke for most of 

 its length and then expands suddenly to form the prominent basUar 

 lobe; the outer shaft arises as a rod-like structure not materially 

 stouter than the inner lobe, and for one-third its length is directed 



