Insects of Shade Trees and Their Control. 93 
ege starts and stimulates the growth of the gall around it. The grub 
which hatches from the egg is footless, creamy or white in color, 
and feeds, grows, and transforms to the adult four-winged fly in a 
cell in the gall and then bores its way out into the open. 
The gall gnats.—The ‘adult insect is usually a rather small, two- 
winged gnat, seldom recognized by other than entomologists. In the 
course of flight the eggs are laid on the surface of the object of attack, 
which may be leaf, flower, fruit, bud, or stem. Wherever the egg is 
Inid the tissue around it reacts by producing an unusual growth 
culminating in a closed gall wherein the creamy, greenish, yellowish, 
or pinkish maggot feeds and may be found while the gall is still green. 
The pupa is formed within the gall, or else the maggot, upon reach- 
ing full growth, drops to the ground and there transforms to the pupa 
and subsequently to adult fly. There is apparently only one genera- 
tion a year in most of these flies. 
Remedy.—Where some action is imperative—and this ean only 
be true of very highly prized trees after several years of repeated 
infestation—cutting and burning of gall-laden wood or fallen leaves 
while the insects are still within the galls is bound to result in con- 
siderable benefit if the work is carried out on the infested oaks of a 
sufficiently extensive area. 
RED SPIDERS.” 
Character and extent of damage—During a protracted drought the 
red spider is likely to become very injurious, attacking a great va- 
riety of plants. Whole trees, especially seedlings and nursery stock, 
are apt to have their foliage killed by it. 
Evidence of infestation—Pale brownish spots which may later 
cover the foliage of the entire plant and a web sometimes so dense as 
to be plainly visible at a considerable distance appear on the leaves. 
On examination with a magnifying lens the affected leaves are found 
to bear numerous, tiny, pearl-like eggs, brownish or reddish little 
creatures running about, or the glistening empty eggshells and cast 
skins of the mites. 
Seasonal history and habits—“ Red spider” is the name most often 
applied to two species of web-spinning mites. Mites differ from true 
insects in having four pairs of legs in the adult stage (fig. 64). 
They pass the winter as adult females on various wild plants. In the 
spring they ascend plants and start egg laying at the rate of 5 to 10 
eggs a day for a period of 8 to 12 days. During hot, dry weather 
the eggs hatch, in about 4 days after having been laid, into young 
mites which commence feeding almost immediately. They reach ma- 
turity in 10 to 14 days after hatching, depending on the season and 
locality. Many ‘generations follow one another in the course of one 
© Tetranychus telarius L. and spp. 
