26 ON ENTOMOLOGY. 



the water to a dry place, such as a grassy bank or the stems of aquatic 

 plants, into which it pushes its sharp claws and remains for a short time 

 immoveable. By the swelling of the upper part of the body the envelope 

 is soon distended, and bursts asunder on the back of the head and 

 shoulders, and through this opening, first the head and then the legs of 

 the perfect Fly make their exit, while the empty slough of the legs 

 continues fixed in its place. After this first part of the process is accom- 

 plished, it hangs down its head and rests for a space, as if exhausted by 

 previous exertion, or rather to allow the newly excluded parts to dry 

 and become more firm. It next erects itself, and laying hold of the 

 upper part of the slough with its feet, pulls the parts still enveloped 

 further out, then creeping forward by degrees, it disengages the entire 

 body, and again rests for a time immoveable. The wings now begin to 

 expand themselves, and their plaits and folds become gradually smooth. 

 The body, also, becomes insensibly larger and longer, and the limbs 

 acquire their just size and proportions. While the wings are undergoing 

 the operation of drying and expanding, the insect takes care to keep 

 them from coming into contact with the body, by bending itself into the 

 form of a crescent; for if they were obstructed whilst wet, they could 

 not afterwards be set to rights. All these changes are perfected, ac- 

 cording to Swammerdam, by the force of the circulating fluids and the 

 air impelled by respiration, a fact of which there cannot be any doubt. 

 It is very seldom, however, that they can be surprised at the precise 

 moment of their transformation, as it is for the most part very speedily 

 accomplished, for the whole of the preceding evolutions are usually 

 completed in ten or fifteen minutes. It happened by mere chance, says 

 Swammerdam, that I observed for the first time one of these vermicles 

 adhering to a stone-wall in the river Loire (France), and it was so 

 softened by the water dashing up against it, that it could only half per- 

 fect its change, so that I took it partly free and partly fixed in the 

 skin. I once afterwards saw the change in the large kind of Dragon 

 Fly (Eshna), which had crept to land out of a small lake, and cast its 

 skin sitting in the grass. 



H YMENOPTERA is the fifth order of insects. A very curious and 

 interesting genera Cynips, whose nests are found in abundance during the 

 summer on the leaves of the rose-tree, the oak, the poplar, the willow, 

 and many other trees, in the globular form of a body about the size of 

 a currant, and usually of a green-colour tinged with red, like a ripe 

 Alban or Baltimore apple. When this pseudo apple in miniature is cut 

 into, it is found to be fresh, firm, juicy, and hollow in the centre, where 

 there is either an egg or a Grub safely lodged and protected from all 

 ordinary accidents. Within this hollow ball the egg is hatched, and the 

 Grub feeds securely on its substance, till it prepares for its winter sleep 

 before changing into a Gall Fly (Cynips) in the ensuing summer. There 

 is a mystery as to the manner in which this Gall Fly contrives to pro- 



