I50 



ARTHROPODS : INSECTS. 



other insects, and thus destroy great numbers of them. 

 Sometimes the eggs are laid upon the outside, but usu- 

 ally inside. When laid on the outside of the pupje, 

 the Ichneumon, as soon as hatched, eats its way into 

 its victim ; when laid inside, it feeds upon the bod\' 

 but attacks no vital part, and the insect does not die 

 till the Ichneumon is ready for the pupa state. 



Gallflies. 



These are very small Insects, and the females have a 

 long, slender ovipositor, with which they insert their 

 eggs into leaves and other parts of plants. These 

 punctures cause outgrowths called galls, which vary in 

 size, form, and solidity, according to the nature or part 

 of the plant that is wounded, and 

 according to the kind of Gallfly that 

 makes the wound. Some are shaped 

 like an apple, as the gall of the oak ; 

 some like a bunch of currants; some 

 ai f: almost as hard as iron ; and some 

 are juicy and pulpy, like fruit. At 

 length the eggs hatch, and the larvae 

 feed upon the vegetable matter which surrounds them. 

 Some galls have only one tenant, others contain many, 

 and usually these Insects undergo all their changes 

 within the galls, and, gnawing through the shell, fly 

 away ; but some kinds gnaw through at the end of 

 their larva life, and enter the ground to go into the 

 pupa state. The nutgalls used in making ink, in col- 

 oring, and in medicine, are caused by an insect which 

 punctures a species of oak common in western Asia. 

 The Rosebush Gallfly punctures the stems of rose- 



