I So TRANSFORMATIONS OF INSECTS. 



growth, it makes a very woody cocoon, and sticks it to the twigs 

 of the tree upon the leaves of which the insect lives. The cocoon is 

 brown and very hard, and the larva hybernates in it, and is trans- 

 formed in the spring. The fly gnaws off the top of the cocoon 

 from within, and escapes ; its jaws, like those of most others, 

 being made solely for this purpose. The Tom-tits get a great 

 many of the larvae by nibbling the cocoons during hard winters. 



THE HYMENOPTERA WHICH PRODUCE GALLS. 



GALL FLIES {CynipsidceV 



The Hyniaiopteva that produce galls, or excrescences upon 

 plants, form a group by themselves. They are small insects, 

 very distinguishable, and they stimulate a great number of dif- 

 ferent kinds of plants to develop those unusual growths of their 

 tissues which are called gall-nuts, galls, oak-apples, &c. Every- 

 body has seen these curious and odd-looking excrescences ; but 

 very few have noticed the beings that have grown within them — 

 and which, when they have attained their perfect form, escape 

 and fly. A winged insect not much more than a tenth or a 

 twelfth of an inch long is not readily observed, especially when 

 amongst the host of little flies that continually move around us. 



These small Hyincnoptera belong to one family — that of the 

 CynipsidcB — which contains the genus Cynips, and others very 

 much like it. The CynipsidcB have an oblong and very convex 

 body, the abdomen of which is attached to the thorax by a very 

 thin pedicle. The saw ovipositor is very curiously made ; it is 

 very long and slender, and is twisted up in a spiral form within 

 the abdomen of the female when it is not required. But when 

 the insect has made up its mind to lay an egg, having chosen 

 the proper spot, the muscles of the abdomen suddenly unfold 

 this spiral, and the ovipositor is straightened, and thrust instan- 

 taneously into the plant. 



The CynipsidcB are found everywhere in spring and summer. 

 When about to lay, the females take great trouble to seek a 

 good place on a proper plant : they make a puncture with their 

 long ovipositors in a twig or leaf, and deposit either one or a 



