140 MAINK 8TATK COLLEGE 



the iuuer face about four bristles, see Fig. 4. The third joint is 

 not more than half as long as broad(about .Olo m. m. by .03 ra. m.) 

 bearing on the inner side a claw about .02 m. m. long, curved 

 toward the face of joint two, which bears the bristles. There is a 

 free motion between segments two and three, and joints one and 

 two are moveable and opposed to the claw on joint three, making 

 nipping jaws. The structure of the end of the palpus of this 

 species has a striking resemblance to that of T. 6 — maculatus, 

 Riley figured in U. S. Agrl. Report, 1889, pi. II., though the 

 third short joint bearing a claw seems to be absent, or not shown 

 in his drawing. The rostrum or beak is composed of three seg- 

 ments, (see Fig. 4) the basal one composed of two parts, broad 

 at the base and rounded in front, and at the carapace reaching be- 

 yond and covering the base of the palpi. The second joint is 

 short and emarginate in front, terminal segment tongue shaped, 

 obtuse and emarginate in front. Originating beneath the rostrum 

 and extending forward beneath the palpi are two stout hairs. 

 The basal portion of the proboscis is covered by the beak of the 

 carapace. The visible portion is composed of three joints. The 

 basal is broadest and oblong ; the terminal one slender, rounded 

 in front and bearing at the edge two short spines and near the end 

 numerous slender spines. The details of the mandibles we could 

 not make out clearly but think they are rounded and plain on the 

 outer margin, bearing at the end a lobe which projects beyond the 

 end of the proboscis. 



Greenish black spots are usually found on the leaves of plants 

 affected by this mite. Probably this is the reason why Henderson 

 called the disease by the inappropriate name "Black Rust." It is 

 commonly believed that these dark spots are formed from juices 

 of the plants that have exuded from punctures made by the mites 

 and have dried. A careful microscopic examination proved them 

 to be small usually globular masses from .1 m m. to .175 m m, in 

 diameter and composed of spherical elements from .025 to .035 mm. 

 in diameter. These spherules are clear with granular contents, or 

 greenish with a darker centre. A careful comparison of them 

 with the contents of the body of the mites proved that they were 

 excreta. These yellowish, or black balls are often found attached 

 to the fibres of the web in miid air between the points of attach- 

 ment of the web where it stretches across from leaf to leaf or 

 from stem to leaf. This could not possibly occur if they were 

 exudations from punctures. The web running over the surface 

 and dotted here and there with these yellow and black excreta 

 reminds one of aminute erysiphe in different stages of development. 



