1909] Burrill, Epedemic of Silver Maple-Leaf Mite. 127 



still salmon-colored and amidst the fungus ; and, in two cases, the 

 filaments of fungus had apparently borne the dead mite out into 

 the cavity, whether wrapped about it I could not tell. All the 

 fungus was shrivelled. This may prove a chief parasite of the 

 mite both in the trees and perhaps in the leaves on the ground. 

 A tuft of hairs closes the gall opening on the ventral surface of 

 the leaf and it would be easy to mistake, in sections, the shrivelled 

 trichomes for old fungus, were it not for the webbed character 

 of the fungus. On this point Cook (1902, p. 265) says: "Tri- 

 chomes are always found extending from the walls of the cavity 

 (figs. 8-1 1 ) of young galls, but disappear as the galls approach 

 maturity." Describing the histology of these galls in 1904, he 

 speaks of the growing of "convolutions of the parts as in the case 

 of — Phytoptus quadripes (figs. 10, 43) — " which "result in the 

 formation of a more or less well defined cavity, and trichomes 

 are developed in great abundance in the younger stages." The 

 frequent interruption of regular lecture work prevented comple- 

 tion of this study before I moved away from this region, and 

 before I could save material for submission to others for identi- 

 fication of fungus. As shown, the worm was not common, but 

 the fungus was sufficiently so to suggest its possible value as a 

 parasite. However, the restatement of the facts about this spe- 

 cies should point out to others the gaps in our knowledge, the 

 filling in of which may yet lead to an inexpensive treatment of 

 the beautiful and ornamental silver maple. 



BIBLIOGRAPHY. 



Banks, N. 



1905. A Treatise on the Acarina, p. 106, fig. 192, Proc. U. S. 

 Nat. Mus., Vol. 28, No. 1382. 



1907. A Catalogue of the Acarina, p. 621, Proc. U. S. Nat. Mus., 

 Vol. 32, No. 1553. 



Chad wick, G. H. 



1908. Oct. 15. Appendix B. A Catalogue of the "Phytoptid" Galls 

 of North America, p. 124, 121, No. 10, N. Y. Sta. Mus., Bull. 

 124, p. 120-1, reports it on Acer rubrum. Eef. in ib. Bull., 

 134, p. 66. 



Cook, M. T. 



1902. May. Galls and Insects Producing 1 Them. Part I. The Mor- 

 phology of Leaf Galls. 2. Phytoptus Galls, p. 264-5, pi. 18, 

 fig. 10. Ohio Nat., Vol. 2, No. 7, p. 263-278, 



