xxvin LLOYD'S NATURAL HISTORY. 



singular nidus, and the grubs which they produce immediately 

 begin to feed on the substance of the living animal. They do 

 not, however, devour every part indiscriminately, but are 

 taught by a wonderful instinct to abstain from injuring any 

 vital organ, as if aware that their own existence depended on 

 that of their unwilling foster-parent. In consequence of this 

 the caterpillars survive for a considerable time, and sometimes 

 retain sufficient strength to assume the pupa state, in which, 

 however, they invariably perish. But most frequently the 

 grubs arrive at maturity before that change takes place, and in 

 that case they escape from the body of the caterpillar by gnaw- 

 ing a passage through its sides. Having in this way effected 

 their liberation, they arrange themselves round the sides of the 

 caterpillar, which is now so exhausted that it soon dies, and spin 

 cocoons of a fine yellow colour, in which they are transformed 

 into pupae. When the perfect fly is ready to emerge, it pushes 

 open a small lid at one end of the cocoon, and after it has 

 been for a short time exposed to the air it is ready for flight. 



"Other minute Ichneumons deposit their offspring in the 

 eggs or in the pupae of Butterflies, and such numbers are de- 

 stroyed in this way that it is evidently one of the means 

 employed by Providence to keep within due limits a tribe of 

 creatures which, if left to propagate without restriction, would 

 occasion incalculable mischief by destroying almost every kind 

 of vegetable produce." (Duncan?) 



Not only are most Lepidopterous larvae subject to the 

 attacks of perhaps ten or a dozen different species of insect 

 parasites at least, but to those of thread- worms (Gordius\ 

 fungoid parasites of various kinds, and occasionally external 

 parasites, such as acari and even fleas, besides such enemies 

 as birds, earwigs, woodlice, &c. They are comparatively little 

 affected by cold, but very much, as a rule, by damp, though 

 some live in very damp situations, and a few even in the water. 



