264 THE ENTOMOLOGIST. 



rambling would be useless, since the upper cuticle and the 

 parenchyma of the leaf, which constitute their principal food, 

 are always within reach without the trouble of moving. 

 These they consume in a very methodical manner, leaving 

 the lower cuticle entire ; this very soon dies, withers, and 

 turns brown, making the whole tree look as though covered 

 with dead leaves. 



The process of exuviation, or casting of the skin, obtains 

 in this, as in all other larvae. Before it is performed the little 

 slug wanders about the leaf with more freedom of movement 

 than usual ; it is no longer glued, as it were, to the cuticle. 

 After the skin is cast the slug may be seen licking its old 

 coat, an occupation which seems particularly enjoyable. The 

 mandibles are also incessantly and actively at work ; yet the 

 cast clothing does not entirely disappear, although it is 

 certainly diminished : the anterior part seems to be eaten, 

 the hinder part neglected. This observation is made in con- 

 sequence of the well-known propensity of certain lepidopterous 

 larva3 to make a meal not only of the egg-shell from which 

 they have just emerged, but also of the garments, which are 

 from time to time thrown aside in favour of a new suit. What 

 a saving might be effected if we humans could thus utilise our 

 old clothes instead of feeding on beef and mutton, the price 

 of which seems gradually advancing towards a point which 

 will render the use of such viands impossible. The changing 

 of the skin takes place in America five times. I cannot say 

 that five is the number of ecdyses in England, as I have 

 not counted the new suits worn by English slug-worms. At 

 the last change the slug loses its jelly-like surface, and 

 appears in a neat yellow skin without any viscidity. This 

 occurs nearly a month after their first escape from the 

 egg-shell ; the head "and segmental divisions are now quite 

 as perceptible as in any other species of sawfly. Hence- 

 forward it eats no more, but crawls down the trunk of the tree 

 and buries itself in the earth : at the depth of three or four 

 inches, each forms a neat little oval cell, in which to undergo 

 its final changes to a chrysalis and perfect fly. This cell is 

 formed of earth, but is lined and intermixed with liquid glue 

 secreted in the stomach, and ejected by the mouth. This liquid 

 glue is obviously nothing more than silk in a liquid stale, 

 — a preparation with which the larva of nearly every moth. 



I 



