96 
TRANSFORMATIONS OF INSECTS. 
smaller than those of most other larvae, for had they been 
larger, they would have been in the way in the narrow exca- 
vated gallery ; the membranous feet also are short, and are not 
calculated to grasp, but they can adhere strongly to a large 
surface, and their spines form a complete crown. The head of 
the larva is covered with a reddish and hard integument, so 
as to allow a solid foundation for the action of the jaws in 
grinding the dense tissue of the tree. Curiously enough the 
labrum, or lip, is not notched as it is in the leaf-eaters, and 
this fact proves the design that has influenced the development 
of all the other structures. The body has a soft skin, and is 
covered with tubercles and a few hairs, which render the larva 
very sensitive to the touch. The caterpillar produces a small 
quantity of silk, but not enough to make a comfortable resting- 
place for the chrysalis, so it utilises the saw-dust which has 
accumulated during the process of tunnelling and drilling, and 
forms a comfortable and silken cocoon within, and covers it with 
the dust outside. The chrysalis resembles those of the other 
moths in certain respects, but it has an armature which is not 
merely an ornament, but a most useful mechanism, for it helps 
the pupa to crawl. Immediately after the transformation 
into the moth state, the life of the perfect insect is more or 
less endangered, for in traversing the gallery made when it 
was a caterpillar, it might be severely scratched, and its wings 
spoiled. But the enveloping skin of the chrysalis, with its 
spines and sharp points, acts like a suit of armour to the 
Sesia , which has just got its legs into the world. The insect 
drags its body slowly along, and finally reaches the open air, 
and extricates itself and flies away, leaving the skin behind 
stuck in the hole. In the engraving of the metamorphoses of 
Sesia apiformis , the moth on the tree has just escaped from 
the chrysalis case in the hole below. A larva is shown in its 
gallery, and two cocoons also. 
The Zygcenidce have some likeness to the Sesiidce , and are 
very common in southern Europe, some being found, however, in 
France and Great Britain. The moths fly by day, and like the 
sun and the bright flowers ; they are a sluggish set, however, and 
this peculiarity is found in the larva as well. Some of them have 
