49 



Tbese eggs are identical with those heretofore mentioned, and any 

 doubt as to their parentage was removed by the discovery ot several 

 cast skins of the larval and partly-grown mites about and on them. From 

 these eggs was bred a very interesting Tineid moth, a number of larvae 

 of which were found burrowing in and feeding on the eggs. At the 

 time of writing, none of these eggs have hatched. 



Specimens identical with the last were received June 14, 1888, iron: 

 Mrs. H. S. Eeynolds, of Willis, Mont., concerning which she writes: 



I send you a specimen of interest to us and it may be to you. My husband found 

 it on McCarthy Mountain, at an elevation of about 7,000 feet, on living Aspen trees. 

 I at first thought it red snow-plant, but under a glass it proved to be a mass of eggs 

 just hatching. They look like spiders, but have only six legs. 



When received by us but a few dried and shriveled mites could be 

 found. These eggs were as abundant as, and were identical with, those 

 already referred to, collected by Mr. Turner at an even greater eleva- 

 tion on the Sierra Nevada Mountains, in California. 



The tree mentioned is probably the same in both instances and, on 

 the authority of Professor Fernow, is without much doubt Populus trem- 

 uloides. 



The occurrence of the mites in Oregon and Utah is shown by the 

 following: 



May 28, 1889, Mr. E. Shipley, James Valley P. O., Oregon, sent us 

 twigs bearing young and one full-grown mite, and he reported the mites 

 to be ver3^ abundant on boards, stones, fences, and fruit trees. 



July 19, 1880, Professor Comstock found what is evidently the same 

 mite infesting the apple-trees at Salt Lake City, the eggs, young, and 

 nearly-grown mites occurring abundantly on leaves and twigs. On the 

 under side of the leaves, along the midrib, a fine web was spun, be- 

 neath which and attached to it cast skins of the mites were found. The 

 largest of the mites collected at Salt Lake City by Professor Comstock 

 are somewhat less in size than the ordinary adult B. pratensis, and, 

 while evidently having undergone the final moult had not yet reached 

 complete development, ^o variation in structural details occur and 

 they may, with little doubt, be referred to the species under discussion. 



Habits and Life-history. — As would be naturally expected, the wide 

 range of this mite gives it a somewhat variable habit. 



In the more northern regions and at higher elevations the winter is 

 passed principally, if not altogether, in the egg state. The mites, or the 

 last brood (there are evidently several broods) come to maturity in the 

 fall and deposit their eggs on the trunks and branches of the trees fre- 

 quently in sufficient numbers to entirely cover the bark of the trunk and 

 branches to a height of several feet. The young mites issue during 

 March and April following. 



In the cases referred to above of the occurrence of the eggs in Cali- 

 fornia and Montana at an elevation of 7,000 to 8,000 feet, the issuance to 

 the young was delayed, evidently by the cold, till from the 1st to the 15th 



