The carmine spider mite, Tetranychus cinnabarinus (Bois.), is a 
common and widely distributed species that feeds on a great 
many species of plants, trees, and ornamentals. Several genera- 
tions are produced during the summer months, often giving rise 
to tremendous populations. Heavily infested plants may be en- 
tirely defoliated, especially during hot, dry weather. T. ellipticus 
Garm. is often abundant on honey locust in the Midwest. T. 
homorus P. & B. feeds on hickory and ash in North Carolina; 
T. magnoliae Boud. occurs on magnolia and yellow poplar in 
Louisiana; the four-spotted spider mite, 7. canadensis (McG.), 
feeds on elm, basswood, horse chestnut, osage orange, and poplar 
throughout eastern United States and southern Canada; and the 
Schoene spider mite, 7. schoenet McG., infests elm and black locust 
throughout eastern United States. 
The genus Hotetranychus also contains a number of common 
and frequently important species. E. populi (Koch) and E. wel- 
dont (Ewing) are found on poplars and willows; E. hicoriae 
(McG.) occurs on pecan, hickory, horse chestnut, and various 
oaks; and E.. matthyssei Reeves attacks elm in New York. Heavy 
infestations may cause severe browning and cupping of the under- 
sides of leaves. EF. querci Reeves has caused severe browning of 
pin oaks in New York. 
Platytetranychus multidigituli (Ewing) feeds on the leaves of 
honey locust, causing them to turn yellow, and P. thujae (McG.) 
attacks arborvitae, juniper, and cypress. Eurytetranychus buxi 
(Garman) is a serious pest of European boxwood. The leaves of 
infested plants become bronzed, then wither and sometimes fall 
prematurely. 
The family Eriophyidae contains a number of tree-infesting 
species (414). Many produce open pouch-like or blister-like galls 
on the twigs and leaves of their hosts. Some cause a rusting of 
infested leaves, and certain others feed on buds. A few of the 
more common and important tree-infesting species are discussed 
here. 
The maple bladder-gall mite, Vasates quadripedes (Shimer), is 
a common species. It ranges in length from about 1/20 to 1/5 of a 
mm. and feeds on the under-surface of silver maple leaves, caus- 
ing the formation of pouch-like or bladder-like galls up to 3 mm. 
in diameter (fig. 1). At first, these galls are light colored or 
yellowish green. Later, they are reddish to almost black and look 
for all the world like miniature green peppers standing on stalks 
above the leaf surface. Heavily infested leaves are often distorted. 
The related species, V. aceris-crummena Riley, produces slender, 
fusiform, or spindle-shaped galls about 5 mm. long on the upper 
surfaces of silver and sugar maple leaves. 
A few of the other eriophyids infesting trees and some of their 
hosts are as follows: Eriophyes fraxiniflora Felt—feeds in the 
staminate flowers of ash. Infested clusters become deformed and 
remain on the tree as green masses until fall. The pear leaf blister 
mite, EZ. pyri (Pagen)—an introduced pest of pear and apple, has 
also been recorded on mountain ash and shadbush. It is sometimes 
abundant enough on mountain ash to cause noticeable injury. E. 
parapopuli (K.)—stunts the growth of poplar by producing 
woody galls around the buds. EH. caulis Keifer—causes large, de- 
forming, hairy growths on the petioles of black walnut leaves. The 
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