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Almost all of the above named insects are sufficiently numerous at 
times, when working alone, to kill or at least to greatly retard the 
growth of the tree or trees upon which they feed. Of course, they do 
not all occur at once in any given locality in such overwhelming num- 
bers, nor are the injuries the same every year; but quite frequently 
two or more of the species are found feeding in company upon the same 
tree in numbers sufficiently greatto do harm. In addition to the species 
named above there are a great many others that are also known to at- 
tack and injure the trees growing upon tree-claims; but these latter 
have not yet made their presence so strongly felt as to force us to place 
them on the list of insect pests in connection with tree-claim culture. 
For a description and life history of many of these the reader is referred 
to Bulletin No. 7 of the United States Entomological Commission, en- 
titled ‘ Insects Injurious to Forest and Shade Trees.” 
Causes for these Insect Injuries.—There is a cause for everything, so 
in the present instance we must look for one or a combination of causes 
that work together in producing the undue increase of insect life upon 
the prairies when new varieties of plants are introduced. A very 
superficial survey of the ground will quickly reveal tous some of these 
causes. 
In the first place, there are always a few dwarfed trees of most of the 
kinds that are usually planted upon claims. These trees are scattered 
along the water courses, in ravines and gulches, and afew other localities 
that are protected from the fires which have annually swept over the 
broad prairies for generations. These few trees furnish food for small 
colonies of the various species of insects that we have named. There 
are always enough of them to very quickly stock aclaim close by upon 
which small trees are planted that are to their taste. Then, too, all of 
these injurious insects are of a hardy nature, used to a precarious life, 
and are strong fliers capable of making comparatively long journeys in 
search of food for themselves and their progeny. They are, in fact, the 
nomads of the insect world, capable of withstanding the vicissitudes 
belonging to a life upon the vast prairies where the more delicate para- 
sitic forms could not live or even find shelter. Then, too, their 
requirements for quarters in which to pass the long, cold winter months 
are less complex than are those of the species that come later on. 
In the second place, the country being destitute of groves of timber 
among the branches of which insectivorous birds can find shelter and 
build their nests most of these insect destroyers are absent. Of course, 
the absence of so great a factor as are these birds in the ridding a 
country of its insect pests soon becomes apparent in the increase of the 
latter and of the accompanying injury done by them. The absence of 
groves, too, not only keeps away the feathered tribe, but also prevents 
many of the more delicate parasitic and a large number of the preda- 
ceous insects from becoming established in the region. The majority 
of these latter forms of insects, as before stated, are such as require 
ptii—: ni 
