I.:4 INDIRECT BENEFITS DERIVED FROM INSECTS. 



pierces its wall, however thick, and commits the destroying 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. Marwick 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 oi Ichneumon^ 

 know how to oviposit it in stercorarious larvae without soiling their wings 

 or bodies. 



The ichneumonidan parasites are either external or internal. Thus the 

 species above alluded to, which attacks s[)iders, docs not live within their 

 bodies, but remains on the outside** ; and the larva of Opliion luteum, 

 which adheres by one end to the shell of the bulbiriferous egg that pro- 

 duced it, does not enter the caterpillar of Euprepia vUlica, the moth upon 

 which it feeds.^ 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 larvje of Pontia 

 BrassiccB) which Reamnur put into a glass to feed, twenty-five were fatally 

 pierced by an Ichneumon (^Alicrogaster globatus*). And if we compare the 

 myriads of caterpillars that often attack our cabbages and brocoli with the 

 small number of butterflies of this species which usually appear, we may 

 conjecture that they are commonly destroyed in some such proportion — a 

 circumstance tliat will lead us thankfully to acknowledge the goodness of 

 Providence, which, by providing such a check, has prevented the utter 

 destruction of the Brassica genus, including some of our most esteemed and 

 useful vegetables. 



The parasites are not wholly confined to the order Hyvicnoptcra : a 

 considerable number are also found amongst the tribe of flies, many of the 

 species of the Dipterous genera Tackina Meig. ; and those separated from 

 it (as Echinomyia, Nemorcea, &c.), as well as oi Anthrax ^^x\A other genera 

 depositing their eggs in caterpillars and other larvae, often in such great 

 numbers, that from a larva of Sphinx atrojjos, bred by M. Serville, and 

 which had sufficient strength to assume the pujia state, not fewer than 

 eighty flies of Senometojna atropivara came out of it.^ Many beetles also 

 are parasitic in their larva state, as the singular Rtpiphorus 2)(nr/doxu.s; 

 which is found in the nests of wasps ; those of the genus Sitaris, which are 

 found in the nests of wild bees of the genus Anthophora '', and those of 

 Brachytarsus scabrosus, which feed on CoccidcB'^, &c. 



* Alysia Manducator ; and another species allied to Alomyia Debellator, which I 

 have named A. Stercorator. 



2 De Geer, ii. 863. 3 jbiJ. 851—855. 



4 Eeaum. ii. 419. 



^ Macquart, Dipteres, ii. 105. Comp. De Geer, i. 19G. vi. 14. 24. Eeaum. ii. 

 440—444. 



6 Ann. Snc. Ent.de Frnnce,Ym. Bull. xvii. xlvii. Much obscurity exists as to 

 the economy of these insects, chiefl}'' in consequence of the curious facts observed by 

 my friend M. Pecchioli of Pisa with regard to his new species Sitaris solieri, de- 

 scribed by him in the Ann. Soc. Ent. de France, viii. 5. 27. He always found both 

 sexes of this species, even in distant localities, on plants of rosemary ; and these 



Tor note ^ see p. 455. 



