228 AFFECTION OF INSECTS FOR THEIR YOUNG. 



drawn from the nectary of a flower. This, therefor^ or its neighborhood, 

 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 recognizes 

 the desired plant the moment she approaches it, and upon this she places 

 her precious burden ; yet not without the further precaution of ascertain- 

 ing that it is not pre-occupied by the eggs of some other butterfly ! Hav- 

 ing fulfilled this duty, from which no obstacle short of absolute impossi- 

 bility, 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 larvK of the gad-fly (^(Estrus 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 conveyed into 

 the mouth, and thence find their way into the stomach. But here a ques- 

 tion 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 depos- 

 ited 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 provident 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 ?^ 



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 



' Clark in Linn. Trans, iii. 304. 



