Figure 26.—Leaf of the soft-maple (Acer dasycar- 
pum), showing the galls produced by Phytoptus 
quadripes. H. Garman, del. 
The galls are quite as peculiar as the hairs, and assume the 
greatest variety of forms. On the same plant this variation is not 
wide, although there is great irregularity in outline and in size. 
They may be distinguished from similar galls produced by dipterous 
insects in that they always have an opening by means of which 
the mites can pass in and out. ‘This opening is usually on the 
under side of the leaf, and consists of a narrow slit or puckered 
orifice, frequently almost obliterated by the closing together of the 
margins, or concealed by a tuft of hairs similar to those described 
as forming mats on the exposed surfaces of the leaves. 
They consist of portions of the leaf which an unusually rapid 
growth has caused to swell upward, thus forming a little pouch in 
which the mites live. Since the attack is begun on the under side 
of the leaf, these pouches project from the upper surface and have 
the opening below. They stand up from the leaf like ten-pins or 
tops, or form wart-like execrescences, in some of which the projec- 
tion is equal on both sides of the leaf. The size will average in the 
neighborhood of a tenth of an inch. ‘The outer surface may. be 
clothed with scattered hairs, smooth, or irregularly wrinkled, or pitted. 
The colors change with age and differ with the plants. At first most 
of them are like the leaves on which they grow in color, later becom- 
ing purple, yellow or some shade of brown, and finally blackening 
and drying up. 
