INSECTS. 
12 
mastication of food, for digging holes in the ground or for gnawing timber and 
various other purposes. In some ants the soldiers have the head enormously 
developed, as are also the mandibles; their function being to protect the society 
from enemies, and also to carry on war against neighbouring communities. The 
antennae are in most cases long, jointed, and filiform, constituting sensitive organs of 
touch and recognition. The thorax is composed of the usual three pieces, 
prothorax, mesothorax, and metathorax. It bears the wings, four in number, 
above, and the legs, six in number, beneath, the latter being modified in many 
species for special purposes, such as, in the bees, for gathering pollen from the 
blossoms of the plants visited for the sake of honey. Often the legs are armed with 
long spines, which in the sand-wasps materially assist in the excavation of the 
pits in which these insects bury their victims and deposit their eggs. The wings 
are ample, strong, and light, formed of a transparent membrane strengthened 
with fine nervures or veins. The arrangement of these nervures varies much 
in different groups, and is of importance in the classification of members of the 
order. The relative importance of this character is, however, not the same in 
every family, being in the saw-flies, perhaps, of the greatest value. Species which 
are wingless in one or both sexes are found in many of the families ; while in the 
genus Oxyura of the family Proctotrypidce the wings consist merely of a fine 
central stalk with a battledore-shaped plumose tip. The abdomen is united to the 
metathorax either throughout its whole width, as in the Tenthredinidce, or, as in 
most of the other families, by a narrow stalk or petiole. These two characters 
serve for the division of the order into the groups of Sessiliventres and Petiolata. 
The organs of reproduction are situated at the apex of the abdomen; while in the 
female the instrument for depositing the eggs has become in the section Aculeata 
developed into a sting; in the Ichneumonidce it is sometimes enormously long, and 
used for piercing the larvae in which they lay their eggs. In the case of the large 
wood-borers ( Sirex ) it is used as a boring instrument, while in the saw-flies it is 
serrated on the edges and employed to wound the tender shoots on which the 
eggs are deposited. Amongst the Pompilidce and some other families, the sting 
is used to paralyse the victim in which the insects lay their eggs, or leave in the 
cell to feed the larvae as they hatch. Probably no pain is given to the victim, 
and even in the case of those grubs that feed internally upon the tissues of 
caterpillars in all probability less inconvenience is caused than we suppose. 
In all cases the metamorphosis is complete. The egg may be laid in a cell 
prepared either by the female or the workers for the purpose, and the grub is fed 
by the attendants on a preparation of pollen or other foods specially prepared. 
In other cases the eggs may be laid on the foliage of trees and plants on which 
the larvae feed, or they may be deposited upon or in the bodies of living or 
paralysed caterpillars, grubs of other species, or spiders, locusts, and the like. 
The Cynipidce with the poison from their sting, and other causes combined, 
produce a large gall upon the leaves of trees, especially oaks; and on the fleshy 
cell-structure of these galls the grubs feed when they emerge. Larvae of two 
different kinds are met with in the order. Thus, whereas those of the saw-flies 
have legs, sometimes even more in number than those of the Lepidoptera, the 
grubs of the majority lack functional legs. The former live a life of greater 
