INDIRECT BENEFITS DERIVED FROM INSECTS. 269 



that destroys it a . In vain does the destructive Cecido- 

 mi/ia of the wheat conceal its larvae within the glumes 

 that so closely cover the grain ; three species of these 

 minute benefactors of our race, sent in mercy by Heaven, 

 know how to introduce their eggs into them, thus pre- 

 venting the mischief they would otherwise occasion, and 

 saving mankind from the horrors of famine 5 . In vain 

 also the Cynips by its magic touch produces the curious 

 excrescences on various trees and plants, called galls, 

 for the nutriment and defence of its progeny : the para- 

 site species attached to it discovers its secret chamber, 

 pierces its wall however thick, and commits the destroy- 

 ing egg to its offspring. Even the clover-weevil is not 

 secure within the legumen of that plant ; nor the wire- 

 worm in the earth, from their ichneumonidan foes. I 

 have received from the late Mr. Markwick that of the 

 former, and Mr. Paul has shown me the destroyer of the 

 latter, which belongs to Latreille's genus Proctotrupes. 

 Others are not more secured by the repulsive nature of 

 the substance they inhabit ; for two species at least of 

 Ichneumon know how to oviposit it in stercorarious 

 larvaB without soiling their wings or bodies. 



The ichneumonidan parasites are either external or 

 internal. Thus the species above alluded to, which 

 attacks spiders, does not live within their bodies, but 

 remains on the outside d ; and the larva of Ophion luteum, 

 which adheres by one end to the shell of the bulbiferous 

 egg that produced it, does not enter the caterpillar of 

 Euprepia villica> the moth upon which it feeds 6 . But 



a Marsham in Linn. Tram. iii. 26. b See above, p. 169-170. 

 c Alysia Manducator ; and another species allied to Alomyia De- 

 bcttator, which I have named A. Stercorator. 



a DeGeer, ii. 803. * Ibid. 851-5. 



