261 



appears to be composed of silk and particles of frass. They remain 

 in the larval stage until the end of February, when pupation begins, 

 and the adults emerge in March. MacGillivray's description of the 

 adult is appended. 



Wilson (H. F.). Injurious Gall Mites; pp. 123-126, 4 figs. 



Four species of gall-mites found in Oregon are considered in this 

 paper : viz., Eriophyes pyri, Pagst., (pear-leaf blister mite), E. vitis, 

 I^and., (grape-leaf mite), E. tristriatns, var. erineus, Nal., (walnut-leaf 

 mite) and E. avellanae, Nal., (filbert-bud mite). 



E. pyri winters about the bud scales of the plant's young growth, 

 usually about the second or third scale from the outside. When 

 abundant, they are found in colonies of fifty individuals or more, 

 protected by the pubescence which is usually present. As the buds 

 swell and the leaves open, the adults spread over the under surface 

 of the leaves and each female burrows through the epidermis and into 

 the parenchyma of the leaf, where it deposits its eggs. As the young 

 develop they extend the channels in all directions, causing the develop- 

 ment of a corky gro^\i;h. Throughout the season the adults are 

 spreading over the leaf-surface and forming other galleries, with the 

 result that in summer or autumn the leaf may be one mass of these 

 blisters. In such cases, the vitality of the tree is seriously impaired. 

 The spots caused by this mite resemble very closely those formed 

 bv various fungi, but examination with a lens of the under side of the 

 leaf will reveal a small round hole leading to the burrow within, which 

 is characteristic of all mite blisters. This mite attacks the leaves 

 not only of the pear, but of apple, ha^\i;horn, quince and other trees. 

 No serious injury is done to these, although a closely related species 

 is beginning to work on the apple in the eastern United States. The 

 results obtained in the North-west by spraying with lime-sulphur just 

 before the buds start, have been quite satisfactory. Probably, when 

 spraying for these insects alone, better results would be obtained by 

 spraying at the time when the mites are migrating from the leaves 

 to the buds. Experiments conducted in New York indicate that the 

 best results are obtained by using an oil spray such as Scalecide, 

 distillate, or. kerosene emulsion. The author has always recommended 

 lime-sulphur, winter strength. 



Specimens of leaves containing galls of E. vitis were received wdth 

 a note to the effect that the vines were badly infested, but apparently 

 not suffering to any extent. Nothing is known of its life-history, 

 but the mites almost certainly hibernate as nymphs or adults about 

 the bud scales or under loose bark. They should therefore be easily 

 destroyed by lime-sulphur or an oil emulsion spray applied during 

 the dormant season, or just as the buds are swelling in the spring. 

 This species works on the under side of the leaf and causes the upper 

 surface to become distorted with a series of swellings. On the lower 

 side of the leaf opposite these swellings, numerous fine pubescent 

 hairs are caused to grow, which form a felt-like layer. On account of 

 this, this tvpe of gall is commonly known as a felt gall. 



E. tristriatus, var. erineus, another erinose or felt mite, attacks 

 the leaves and nuts of the English walnut, but as the life-history and 

 habits are probably the same as those of E. vitis, lime-sulphur appUed 



