1 86 TRANSFORMATIONS OF INSECTS, 



victim. If two or three eggs had been laid, and larvse 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 IcJmemnon 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 &^^. On the other hand, a very small parasite Avould 

 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 larvae are the structures which protect 

 them, like an armour, from the sudden and eventually fatal stab 

 of the IdinciLmons. 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. 



Larvse are especially subject to the attacks of the parasitic 

 Hyrncnoptera, 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 Ichncumo?is. The life of adult insects is usually brief, 

 and is cut short by many accidents, so that were the larvae 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 Coleoptcm, which are well covered with a hard integument, 



