Chapter 14. 
INJURIOUS INSECTS. 
General observations on Insects and their feeding habits. 
Insecticides and their use. Earwigs. Destructive Caterpillars 
of Cabbage Butterflies, and the Currant, Winter, and Codling 
Moths. The Gooseberry Saw-fly. The Pea Thrips. Wireworms. 
The next class to be considered is that of the INSECTS 
(9), (10),* and, viewed from our present standpoint, they 
are of greater importance than the whole of the rest of 
the Animal Kingdom. Insects can be readily recognised 
by the presence of a pair of antennae or feelers, six pairs 
of legs, and the division of the body into head, thorax 
and abdomen. Either one or two pairs of wings are almost 
always present in adult Insects. The most remarkable 
feature in their life-history is the fact that they pass 
through a series of changes which we term metamorphosis. 
On hatching from the egg, the first stage is the larva, 
which is succeeded by that of the pupa, and from the 
latter emerges the perfect Insect. In many Insects, how- 
ever, the pupa is absent, and then there is a gradual growth 
from the larva to the perfect Insect. Larve are variously 
known as caterpillars, maggots, or grubs, and, being 
exclusively concerned with feeding, they are as a general 
rule more destructive than the perfect Insects. The pupa 
or chrysalis is purely a resting stage, no food is taken, 
and during this period the organs and tissues of the future 
‘Insect are gradually built up. It is of great importance 
* The numbers in brackets refer to the literature given at the end 
; of the final lecture. 
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