24 NATURAL HISTORY. 



and other artificial or dried produce. Many of the caterpillars of the smaller Moths burrow in the 

 leaves of trees, forming galleries or blotches, easily perceptible from their paler colouring. This habit 

 is not confined to the small Moths. Some larger species, such as the Green Foresters (I no statices, 

 &c.), are miners when young, and the larvae of many two- winged flies mine in leaves in the same 

 manner. Some few caterpillars produce galls, and others inhabit cases resembling those formed by 

 the larvae of the Caddis-flies, which they construct out of bits of twig, leaves, or grass. The cater- 

 pillars of the Clothes-Moths actually clothe themselves in a tight-fitting jacket, open at both ends, 

 which they enlarge when necessary. 



During this stage of its existence the insect has nothing to do but eat, and it grows very rapidly. 

 When its skin becomes too small it is cast off, even the skin of the head and the lining of 

 some of the internal organs being thrown off with the rest. Most caterpillars moult four or five 

 times, although some moult only twice, and others as many as six or seven times. So serious an 

 operation is necessarily attended by temporary weakness and discomfort, but the caterpillar soon 

 recovers itself, and begins to eat again as fast as ever, frequently devouring its own cast-off exuviae, 

 before it returns to its ordinary food. The colour and markings, and even the very structure of the 

 caterpillar, are frequently changed after moulting. 



Caterpillars are exposed to many enemies. The most formidable are the Ichneumon Flies, which 

 pierce their skins, and lay an egg in each wound. These eggs soon hatch into small larvae, which live 

 inside the caterpillar, feeding on the fatty portions of its body, but avoiding all the vital parts. 

 When they have arrived at maturity, they emerge from the skin of the caterpillar and form their 

 cocoons round its dead body. Sometimes the caterpillar lives to assume the pupa state, and the 

 Ichneumon Flies come to maturity within the pupa skin. In their perfect state they are flies, with 

 four transparent wings and a slender body, terminated by a long ovipositor. Birds, wasps, and 

 insectivorous animals in general destroy many caterpillars, notwithstanding the various means of 

 defence or concealment possessed by the latter, which are sometimes truly extraordinary. 



One of the most remarkable cases of protective resemblance on record was observed by Mr. 

 Bates on the Amazons. A large caterpillar stretched its head out of a bush, and startled him by 

 its resemblance to a small venomous Snake. He did not succeed in rearing it, but it was perhaps 

 the larva of one of the Sphingidce, for these are large, smooth, and often adorned with very 

 bright colours, such as stripes, bands, and eye-like spots. 



As the larva approaches maturity it becomes possible to trace the outline of the future Butterfly 

 or Moth beneath the skin, and traces of the wings appear just before the larva is ready to assume the 

 pupa state. The silk-glands also become greatly enlarged in most larvae when the time approaches 

 for their metamorphosis. They then consist of two long tubes, opening into the spinneret, and 

 closed at the opposite end. They are sometimes much twisted and convoluted, and extend towards 

 the hinder end of the body, partly above and partly below the intestines. The number of convo- 

 lutions depends upon the length and size of the glands, and in many Butterflies and Moths, which 

 spin only slight cocoons or none at all, the glands are even shorter than the body of the larva, and 

 are only curved twice. These glands are generally of a shining white colour, and can easily be 

 distinguished from the dusky anastomosing tracheal vessels which lie above them. These organs 

 have fulfilled their functions when the insect has assumed the pupa state, and dwindle away so 

 rapidly that after a few days they are reduced to a mere thread. 



When the caterpillar is full grown, and is ready to assume the pupa state, it ceases to eat, and 

 its colours generally fade. Sometimes it remains motionless for several hours or days before it 

 commences the difficult and arduous task of pupation, which is effected in various ways. 



The small Tortoiseshell Butterfly ( Vanessa urticoe) may be taken as typical of those Lepidoptera in 

 which the pupa is suspended freely by the tail. When the larva is about to undergo its metamorphosis, 

 it selects a position which it deems suitable, and commences by spinning a little button of silk, strong 

 enough to support the weight of its body. Having completed this work, the larva thrusts its claspers 

 into the middle of the silk button, which projects a little, and swings itself head downwards from 

 this support. The most difficult part of the whole process has now to be accomplished the 

 extrication of the pupa from the old larva-skin while the latter is thus suspended in mid-air. The 

 larva contracts its body several times until the skin cracks along the back, and the pupa gradually 



