>-1 THE- WHEAT FLY 325 



Devoured by the ichneumon tipula. 



have been observed in which even a fourth of 

 the grain was either destroyed, or very materially 

 injured by them. The late sown wheat always 

 appeared the most infected, arising, no doubt, 

 from the seed of that sown earlier obtaining too 

 great a degree of hardness, before the insects 

 come out to be liable to be much hurt by them. 

 The female lays her eggs by means of a long 

 retractile tube, which unsheaths an aculeus as 

 fine as a hair, and very long. 

 4 These insects would soon become seriously in- 

 jurious, were not their race kept within due 

 bounds by several natural enemies, some of 

 which devour them, and others, particularly the 

 ichneumon tipulae, deposit their eggs in the 

 larvae, the young of which, when hatched there, 

 find a proper nourishment in the bodies of their 

 hosts. This ichneumon is about the size of the 

 wheat-fly : and in order to observe the manner of 

 the female's depositing her eggs in the caterpil- 

 lars of the wheat fly, the Rev. Mr. Kirby, as we 

 are informed, placed a number of the latter on a 

 sheet of white paper, and then set an ichneumon 

 down in the midst of them. She soon discovered 

 one of the larvae ; when vibrating her antennae 

 in an intense degree she fixed herself upon it, 

 and, bending her abdomen obliquely under her 

 breast, inserted her aculeus into the body of her 

 victim, (which seemed by its motion to experi- 

 ence a momentary pain,) and there deposited a 

 single egg. This being done, she went to a se- 



