BENEFITS CONFERRED BY THEM. 41 



vain, also, might we add, does the sand-wasp 

 excavate her deep cell for her young ones ; for 

 when once the ichneumon has discovered the 

 retreat, the destruction of the young larvae is 

 inevitable. She pierces through the defences 

 piled over the mouth of the cavity, with all the 

 precision and patience of a higher creature, and 

 rests not until she has thrust down her long 

 ovipositor, and placed the egg in the body of the 

 helpless prisoner below, when she flies away, con- 

 fident that the days of her victim are numbered, 

 and having thus doomed him to be eaten up alive ! 

 The common caterpillar, which, by its ravages in 

 our cabbage rows, makes itself a little too familiar 

 to us, has a fierce enemy in these flies; they dart 

 upon it, pierce its body in many places, laying an 

 egg in each wound; these in due time become 

 hatched, and eat their way out of the body of the 

 poor caterpillar, who soon dies, while the Iarva3, 

 after undergoing their proper transformations, 

 become perfect insects themselves, fully equipped 

 to proceed to the same w r ork in some other indi- 

 vidual of the caterpillar kind. 



To man, this ordinance of the Creator, that 

 some insects should lay their eggs in the bodies 



