266 INDIRECT BENEFITS DERIVED FROM INSECTS. 



parasite species attached to it discovers its secret cham- 

 ber, pierces its wall however thick, and commits the de- 

 stroying 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. Mark wick 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 

 larvee without soiling their wings or bodies. 



The ichneumonidan parasites are either external or 

 internal. Thus the species above alluded to, which at- 

 tacks spiders, does not live within their bodies, but re- 

 mains on the outside b ; and the larva of Ichneumon lutcus, 

 which adheres by one end to the shell of the bulbiferous 

 egg that produced it, does not enter the caterpillar of 

 Bombyx villica, the moth upon which it feeds c . But 

 the great majority of these animals oviposit within the 

 body of the insect to which they are assigned, from 

 whence, after having consumed the interior and become 

 pupae, they emerge in their perfect state. An idea of 

 the services rendered to us by those Ichneumons which 

 prey upon noxious larvae may be formed from the fact, 

 that out of thirty individuals of the common cabbage 

 caterpillar (the larva? of Papilio Brassicce) which Reau- 

 mur put into a glass to feed, twenty-five were fatally 

 pierced by an Ichneumon (Z globaftis A ). And if we 



a I. Manducator, Pauz. Fn. Germ. 72. 4. ; and another species al- 

 lied to I. Dehellator, F., winch I have named /. Stercorator. 



b De Geer, ii. 863, c Ibid. 851.5. d Reaum. ii. 41 9, 



