INDIRECT BENEFITS DERIVED FROM INSECTS. 267 



Lndividual varies according to its sige, and that of the* 

 grubs which are to spring from them ; being in most cases 

 one only, but in others amounting to some hundreds. 



From the observations hitherto made by entomolo- 

 gists, the great body of the Ichneumon tribe is princi- 

 pally employed in keeping within their proper limits 

 the infinite host of lepidopterous larvas, destroying, 

 however, many insects of other orders ; and perhaps if 

 the larvae of these last fell equally under our observa- 

 tion with those of the former, we might discover that 

 few exist uninfested by their appropriate parasite. Such 

 is the activity and address of the Ichneumonidce, that 

 scarcely any concealment, except perhaps the waters, 

 can secure their prey from them ; and neither bulk, cou- 

 rage, nor ferocity avail to terrify them from effecting 

 their purpose. They attack the ruthless spider in his 

 toils : they discover the retreat of the little bee, that for 

 safety bores deep into timber; and though its enemy 

 Ichneumon cannot enter its cell, by means of her long 

 ovipositor^ she reaches the helpless grub, which its pa- 

 rent vainly thought secured from every foe, and depo- 

 sits in it an gq^^ which produces a larva that destroys 

 it '*. In vain does the destructive Cecidomyia of the 

 wheat conceal itslarvas within the glumes that so closely 

 cover the grain ; three species of these minute benefac- 

 tors of our race, sent in mercy by Heaven, know how 

 to introduce their eggs into them, thus preventing the 

 mischief they would otherwise occasion, and saving man- 

 kind from the horrors of famine*^. In vain also the Cy- 

 nips by its magic touch produces the curious excres- 



^ Plate XVI. Fig. 1. "^ Marsham in i?»/(. r/vrjis. iii.26, 



■^ Se^* above, p. 172-113. 



