BIBLIOGRAPHY OF APHIDIVOHOUS ICHNEUMONIDiE. 157 



the prevalence of natural enemies tend more to the 

 destruction of insect pests than any artificial methods 

 that yet have been devised. Perhaps we might avail 

 ourselves, more than we do at present of these para- 

 sitic checks on redundant life. Thousands of Bhopalo- 

 siphum nymplicece may often be found on the water- 

 plaintain, 90 per cent, of which, perhaps, are attacked 

 by Allotria or other Ichneumonidje. Such leaves 

 might be introduced into gardens and green-houses 

 with marked beneficial effects, since the emerging 

 parasites do not seem to be confined to preying on 

 single specific forms. In the same manner colonies of 

 the common Siplionophora Sonchi often have far more 

 numerous infected than whole members in their com- 

 munity, and these former might be used for a similar 

 purpose. 



A cliange of form occurs in an Aphis after it has been 

 struck by an Aphidius or Allotria ; but this form does 

 not apparently alter after the insect has sufi"ered a 

 second attack from a Ceraphron or Asaphes. "Walker 

 thinks that suitable Aphides are recognised by Asaphes, 

 &c., by their altered shape, but we do not know how 

 the last insects become aware that an Aphidius- struck 

 Aphis has, or has not been before tampered with by 

 an insect of its own species. 



Bibliography op Aphidivorous Ichneumonid^. 



Haliday on " Parasitic Hymenoptera," vol. i, p. 259, 

 482, of ' Entom. Mag.,' also vol. ii, p. 99. 



Curtis, ' Brit. Entomology and Gruide,' where fifty- 

 four species of Aphidii are recorded, forming the sub- 

 genera Praon, Ephedrus, Toxares, Monoctonus, Tri- 

 onyx, and Aphidius. 



J. Curtis, ' Guide to the Arrangement of Brit. 

 Insects,' 1829. 



Nees ab Esenbeck, ' Hymenop. Ichneum. Afiinium 

 Monog.' vol. ii, 1834. 



