CLASS HEXAPODA. 



79 



FIG. 135. 



ing in that the twig or leaf in which the eggs are de- 

 posited at once begins an abnormal, though characteristic 

 growth, the so-called "galls." The common Oak-apple 

 well illustrates such a gall. Many of the Gall-flies, like 

 the Aphides, are parthenogenetic. 



The Ichneumon-flies (Ik nu'mon), 

 though often microscopic in size, are 

 most valuable as Nature's checks to 

 the inordinate multiplication of other 

 insects. The female searches, until 

 she finds her favorite larva, beneath 

 the skin of which, with her delicate 

 ovipositor, she thrusts several eggs. 



Ich mu'mon man ifes '/I' tor. 

 Ichneumon-fly. 



FIG. 136. 



These, on hatching, 

 feed on the fatty 

 tissues of their host, 

 not attacking the 

 vitals, until they are 

 about to pupate. 

 The unfortunate 

 host thus not only 

 supplies its parasites 

 with food while they 

 live, but finally re- 

 linquishes to them 

 its body, as a sup- 

 port in which they 



are able to undergo their transformations.* 



The common Ants, Wasps, and Bees, excepting the Pseu- 



doneuropterous White Ants, in their intellectual develop- 



* Few larval insects are free from the attacks of Ichneumons. The "grubs" 

 on the inside of solid trees are reached, as are those in the ground, and those 

 under water. Even the larvae of Ichneumons, living as pai*asites, may play the 

 part of hosts to other parasitic Ichneumons, which may in turn he the hosts of a 

 third species of this most interesting group. 



Ichneumon-fly, depositing its eggs in the larvn.- at 

 bottom of the holes. 



