No. 2303. 



RED SPIDERS OF AMERICA— McGREOOR. 



669 



Fig. 7.— Pak.a tetraxychus 

 PRATENSis Banks. 1, tarsal 

 appendages; 2, palpal 

 ••thumb" and its append- 

 ages (original). 



little longer than wide, bearing at its tip a well-developed "finger," 

 whose base is about one-half the width of "thumb" at tip. On 

 upper distal corner of "thumb" are two digituli about half again 

 as long as terminal "finger." On upper side, barely midway to base, 

 is a slender "finger" or sensilla only one-third as thick as the ter- 

 minal "finger," and between this and base are two short hairs. A 

 hair arises latero-ventrally from the center of the "thumb." The 

 claw on the penultimate joint is about as 

 usual. Tip of tarsus bears a very strong, 

 sickle-shaped claw, which is uncleft to its 

 tip. At a point one-fifth its length from the 

 base there arises from the ventral surface six 

 slender spurs in length about two-fifths that 

 of the claw. The usual series of four tenent 

 hairs arise by the sides of the base of the 

 claw. Body length, 0.4 mm. According to 

 Ewmg the form of the penis (see pi. 79, fig. 

 16) is as follows: "Inner lobe slightly over 

 one-half as long as the shaft of the penis. 

 Shaft stout, somewhat similar to the shaft in 

 T. telarius Linnaeus; enlarged slightly at its 

 base, so as to form the basilar lobe. Hook pronounced; bent at an 

 angle of about 90° to the axis of the shaft. Barb absent." 



From Pullman, Washington, on timothy, in June. G. R. Hyslop, 

 coll. 



PARATETRANYCHUS UNUNGUIS (Jacobl). 



Plate 79, fig. 1?.. 

 TetranycMis xinunguia Jacobi. 1905. N-atiu'w. Zeitschr. Land-u., Forst, p. 239. 



Color greenish-yellow, abdomen black mottled through the visi- 

 bility of the excrementary mass. One very long, slender tarsal 

 claw with six widely appendiculate spurs, which are free to their 

 bases, arising ventrally from a protuberance at the base of the claw. 

 Body bristles pointed, not arising from tubercles. Mandibular 

 plate wide, broadly rounded anteriorly without emargination. 

 Penis shaft slender, (see pi. 79, fig. 13) together with acuminate 

 hook, forming a sickel-shaped structure. Eggs round, dark-red, 

 deposited on bark, bud scales, and needles. 



In 1905 Jacobi (12) placed this European species under the then 

 all-inclusive genus Tetranychus, but in 1910 Zacher (13) erected the 

 genus Paratetranychus to include P. ununguis and P. pilosus Canes- 

 trini and Fanzago, based on the tai-sal and collar trachea characters. 

 P. ununguis was described by Jacobi from material on conifer needles 

 collected at Dahlem, Germany. The preferred hosts were Picea 

 sitehnh^is and P. excelsa, of which 30 per cent of the trees were 

 attacked. 



