DESCRIPTIONS OF SEVEN NEW SPECIES OF RED SPIDERS. 



By E. A. McGregor, 



Of the Bureau of Entomology , United States Department of Agriculture. 



Six species of Tetranychus and one of Tetranychina are herein de- 

 scribed for the first time. Two of these from South America and five 

 from North America are of some economic importance. One discolors 

 the leaves of American holly, one injures at times the appearance of 

 the beautiful western white oak, and one saps the vitality of the large 

 huckleberry of the Cascade region. 



TETRANYCHUS PERUUNUS, new species. 



Color, translucent yellowish green. Eyes (in mounted material) 

 clear, directly over front margin of coxae II. Dorsal bristles, 24 in 

 number, not arising from tubercles, for the most part very short and 

 weak, distributed on dorsal aspect of body in about the usual arrange- 

 ment. Body of female rhombic-ovate, widest across hind margin of 

 cephalothorax, which is slightly emarginate in front; male cuneate- 

 pentagonal, widest across hind margin of cephalothorax, which is 

 truncate in front, abdomen tapering to acute point posteriorly. 

 Mandibular plate considerably more than twice as long as broad, 

 margins subparallel, with a very distinct anterior emargination. 

 "Thumb" of palpus very short in proportion to its width, bearing at 

 its tip a relatively large, subconical ''finger," whose base is half as 

 wide as tip of "thumb," length of "thumb" and terminal "finger" 

 together equaling width of "thumb. " On its rather truncate tip, on 

 opposite sides of the "finger," are two stout spines or pseudo-fingers 

 (not much thicker than hairs) ; on upper side, about one-third to 

 base, is a small "finger," and between this and base are two short 

 hairs, the distal-most one of which appears to arise adjacent to the 

 small "finger." The claw on the penultimate joint reaches far beyond 

 the middle of the "thumb;" a hair arises laterally from the center of 

 the " thumb," and another from a similar position on the penultimate 

 joint. The legs are unusually short, in the female distinctly less 

 than the width of the body, in the male barely exceeding the width 

 of body. Femur I considerably less than twice as long as wide, about 

 half again as long as tarsus I. Tibia I just equaling patella I, which 



Proceedings U. S. National Museum. Vol. 51-No. 2167. 



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