AFFECTION OF INSECTS FOR THEIR YOUNG. 193 



has been honey drawn from the nectary of a flower. This, therefore, or 

 its neighbourhood, we might expect would be the situation she would 

 select for them. But no : as if aware that this food would be to them 

 poison, she is in search of some plant of the cabbage tribe. But how is 

 she to distinguish it from the surrounding vegetables? She is taught of 

 God ! Led by an instinct far more unerring than the practised eye of the 

 botanist, she recognises the desired plant the moment she approaches it; 

 and upon this she places her precious burden, yet not without the further 

 precaution of ascertaining that it is not pre-occupied by the eggs of some 

 other butterfly ! Having fulfilled this duty, from which no obstacle short 

 of absolute impossibility, no danger however threatening, can divert her, 

 the affectionate mother dies. 



This may serve as one instance of the solicitude of insects for their 

 future progeny. But almost every species will supply examples similar in 

 principle, and in their particular circumstances even more extraordinary. 

 In every case (except in some remarkable instances of mistakes of instinct, 

 as they may be termed, which will be subsequently adverted to), the 

 parent unerringly distinguishes the food suitable for her offspring, how- 

 ever dissimilar to her own ; or at least invariably places her eggs, often 

 defended from external injury by a variety of admirable contrivances, in 

 the exact spot where, when hatched, the larvae can have access to it. 

 The dragon-fly is an inhabitant of the air, and could not exist in water: 

 yet in this last element, which is alone adapted for her young, she ever 

 carefully drops her eggs. The larvae of the gad-fly (OEstrus equi), whose 

 history has been before described to you, are destined to live in the 

 stomach of the horse. How shall the parent, a two-winged fly, convey 

 them thither ? By a mode truly extraordinary. Flying round the animal, 

 she curiously poises her body for an instant while she glues a single egg 

 to one of the hairs of his skin, and repeats this process until she has fixed 

 in a similar way many hundred eggs. These, after a few days, on the 

 application of the slightest moisture attended by warmth, hatch into little 

 grubs. Whenever, therefore, the horse chances to lick any part of his 

 body to which they are attached, the moisture of the tongue discloses 

 one or more grubs, which, adhering to it by means of the saliva, are con- 

 veyed into the mouth, and thence find their way into the stomach. But 

 here a question occurs to you. It is but a small portion of the horse's 

 body which he can reach with his tongue : what, you ask, becomes of the 

 eggs deposited on other parts ? I will tell you how the gad-fly avoids 

 this dilemma ; and I will then ask you if she does not discover a pro- 

 vident forethought, a depth of instinct, which almost casts into shade the 

 boasted reason of man ? She places her eggs only on those parts of the 

 skin which the horse is able to reach with his tongue; nay, she confines 

 them almost exclusively to the knee or the shoulder, which he is sure to 

 lick. What could the most refined reason, the most precise adaptation of 

 means to an end, do more? 1 



Not less admirable is the parental instinct of that vast tribe of insects 

 already introduced to you by the name of Ichneumons, whose young are 

 destined to feed upon the living bodies of other insects. These, as you 

 know, are so numerous, that scarcely an insect exists, which in its larva 

 state is not exposed to the attacks of one or other of them ; and even the 



* Clark in Linn. Tram. iii. 304. 

 O 



