VORACITY OF INSECTS. ‘147 
vere almost entirely destroyed by the larve of an insect 
alled the “ turnip-fiy.” The parent insects were seen buzzing 
yver the fields, and depositing their eggs in the plants, which 
hey do not themselves employ as food ; and in a few days all 
he soft portions of the leaves were destroyed, and nothing 
yut the skeletons and stalks were left—Some kinds of timber 
yecasionally suffer to no less an extent from the devastations 
f insects, whose operations are confined to the wood, and do 
10¢ manifest themselves externally, until the tree is seen to 
anguish and at last to die. The pine-forests of the Hartz 
nountains in Germany have been several times almost de- 
troyed by the ravages of a single species of beetle, less than a 
yuarter of an inch in length. The eggs are deposited beneath 
he bark; and the larve, when hatched, devour the sap- 
wood and inner bark (the parts most concerned in the fune- 
ions of vegetation) in their neighbourhood. It was estimated 
hat, in the year 1783, a million and a half of pines were 
lestroyed by this insect in the Hartz alone ; and other forests 
n Germany were suffering at the same time. The wonder is 
nereased, when it is stated that as many as 80,000 larve are 
jometimes found on a single tree. 
- 148. But every class in the Animal Kingdom has its car- 
livorous tribes, which are adapted to restrain the too rapid 
merease of the vegetable-feeders (by which a scarcity of their 
ood would soon be created), or to remove from the earth the 
lecomposing bodies that might otherwise be a source of dis- 
aase Or annoyance. The herbivorous races, being for the most 
art very prolific, would very rapidly increase to such an 
: ¢ as to produce an absolute famine, if not kept in: check 
by the races appointed to limit their multiplication. Thus, 
fhe myriads of Insects which find their subsistence in our 
if allowed to increase without restraint, would 
oon destroy the life that supports them, and must then all 
ish together ; but another tribe (that of the insectivorous 
as the woodpecker) is adapted to derive its subsistence 
mm them, and thus to keep their numbers within salutary 
junds. Their occasional multiplication to the enormous 
xtent mentioned in the preceding paragraphs, is probably 
le in general to the absence of the races that should keep 
em in check. This may occur from accidental causes, or 
y be produced by the interference of Man. Thus, a set of 
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