142 



INSECTS HYMENOPTERA DIAGRAM 6. 



and deposits her eggs in the body of the caterpillar. The eggs 

 hatch, and the young larva? feed on the flesh of the caterpillar, 

 which suffers a living death while these larvse devour it. At last 

 it dies, when the larvaB of the ichneumon emerge, and spin round 

 its body the cocoons in which they undergo their metamorphosis. 



The Cynipidos are other small Hymenoptera in which the 

 ovipositor instead of being straight, as in the Ichneumons, is 

 spirally rolled. The ichneumons are serviceable to man by 

 destroying caterpillars ; and the cynipidaa are also useful animals, 



Gall Nut. 



Cynips of 

 the Ink-gall. 



Cynips, magnified. 



but in a different way. They pierce the leaves of trees to lay 

 their eggs there. Where they have pierced the plant, a gall is 

 produced. When it is carefully opened, we always find a number 

 of the larvse of the cynips in the middle. In some countries 

 a great trade is carried on in these galls, because they are used 

 for making black ink. Those which are sold under the name of 

 gall-nuts are produced by a cynips which pierces the leaves of a 

 kind of oak. 



