THE MAPLE GALL-MITE. 



423 



The galls appear with the unfolding of the leaves in spring as slight swellings of 

 the parenchyma, and as the leaf reaches its perfect size they expand usually into 

 top-shaped galls, arising from the upper side of the leaf. The form varies to some 

 extent, some of the galls being discoid or more or less spherical, while occasionally 

 two galls have a common neck and opening. At first the color of the galls is like 

 that of the unfolding leaf, dull purple or green ; later it assumes the light green 

 color of the veins and veinlets; and still later changes, in many cases, to purplish. 

 Towards the end of summer it dries up and becomes 

 black. The outer surface is smooth, but the walls 

 are broadly and irregularly impressed, making a very 

 uneven outline. On the under side of the leaf the 

 position of the galls is usually indicated by an im- 

 pression with a tuft of white hairs in the center, 

 which tuft covers the opening into the gall. Occa- 

 sionally the opening and tuft are borne upon a slight 

 elevation. The height of one of the largest galls, 

 measured from the upper side of the leaf, was .19 inch ; 

 the diameter was .13 inch. The galls are attached at 

 the sides of the veins, and are so numerous on some 



Fig. 154. — Leaf of the soft maple (Acer dasycarpum), show- 

 ing the galls produced by Phytoptus quadripes.—B.. Gar- 

 man del. 



Fig. 155.— Phytoptiig quadripes Shimer. 

 Side view showing the eggs within 

 the body. From a camera lucida 

 sketch. — H. Garman del. 



leaves as to cover the entire upper surface. I have seen trees on which there were 

 very few ungalled leaves, and most of them had curled up and were of a greenish- 

 yellow hue. Three hundred and ten galls were counted on one leaf. Dr. Shimer 

 says thousands occur on some leaves. 



Scores of specimens of the Phytoptus which produces galls on the leaves of our soft 

 maple may be secured in June, in which the eggs with nuclei and nucleoli may be 

 seen with perfect distinctness. 



