186 TRANSFORMATIONS OF INSECTS. 
victim. If two or three eggs had been laid, and larve had been 
born from them, they would have been starved after a while, for 
the body of the infected insect would have been consumed twice 
or three times too quickly. But if a moderate sized parasite 
attacks a tolerably large caterpillar it introduces two or three eggs, 
and if a very small /chneumon meets with a fine larva it may lay 
as many as fifty or sixty eggs in it. There is always enough 
and to spare in these instances, and it would appear that the 
insects considered the future. But there is a great sameness 
in the habits of insects, and these parasites choose their victims 
upon the same plan generation after generation. If the large 
parasite came across a new caterpillar three times as big as any 
it ever saw before, it either would pass it by, or would still only 
lay one egg. On the other hand, a very small parasite would 
always lay the same number, whatever the size of the victim 
might be. | 
All insects are not equally exposed to the attacks of parasites ; 
for instance, those that know how to form shelters are less so than 
those which live in broad daylight on leaves, and hairy caterpillars 
are less liable to suffer than the smooth kinds. It would appear 
that the long tufts of hairs and the branching spines which cover 
the bodies of so many larve are the structures which protect 
them, like an armour, from the sudden and eventually fatal stab 
of the /chneumons. The peculiar movements given to the hairs 
by the contraction of the segments of the body evidently pre- 
vent the parasites from giving the stab with certainty. 
Larve are especially subject to the attacks of the parasitic 
Hymenoptera, and there is no difficulty in understanding why they 
should be chosen as the homes for the future young of such crea- 
tures as the /chnceumons. The life of adult insects is usually brief, 
and is cut short by many accidents, so that were the larve of the 
parasites developed within them, their existence would be con- 
stantly in danger, and very few of them would come to perfection. 
It is very wonderful, however, that those insects which do live 
longer than others in the adult form, should be subject to the 
attacks of parasites, whilst the others, whose existence is in- 
variably short, should never be pierced by the Hymenoptera. 
Many Coleoptera, which are well covered with a hard integument, 
