158 TRANSFORMATION OF ANIMALS. 



Beside their final metamorphosis into flies, caterpillars undergo 

 several intermediate changes. All caterpillars cast or change 

 their skins oftener or more seldom, according to the species. 

 Malpighius informs us, that the silkworm, previous to its 

 chrysalis state, casts its skin four times. The first skin is 

 cast on the 10th, llth, or 12th day, according to the nature 

 of the season ; the second in five or six days after ; the third 

 .^ k in five or six days more ; and the fourth and last in six or 

 seven days after the third. This changing of skin is not only 

 common to all caterpillars, but to every insect whatever. Not 

 one of them arrives at perfection without casting its skin at 

 least once or twice. The skin, after it is cast, preserves so 

 entirely the figure of the caterpillar in its head, teeth, legs, 

 color, hair, &c., that it is often mistaken for the animal 

 itself. A day or two before this change happens, caterpillars 

 take no food; they lose their former activity, attach them- 

 "selves to a particular place, and bend their bodies in various 

 directions, till at last they escape from the old skin, and leave 

 it behind them. When about to pass into the chrysalis state, 

 which is a state of imbecility, caterpillars select the most 

 proper places and modes of concealing themselves from their 

 enemies. Some, as the silkworm, and many others, spin silken 

 webs round their bodies, which completely disguise the ani- 

 mal form. Others leave the plants upon which they formerly 

 fed, and hide themselves in little cells which they make in 

 the earth. The rat-tailed worm abandons the water upon the 

 approach of its metamorphosis, retires under the earth, where 

 it is changed into a chrysalis, and, after a certain time, bursts 

 from its seemingly inanimate condition, and appears in the 

 form of a winged insect. Thus the same animals pass the 

 first and longest period of their existence in the water, another 

 under the earth, and the third and last in the air. Some 

 caterpillars, when about to change into the chrysalis state, 

 cover their bodies with a mixture of earth and of silk, arid 

 conceal themselves in the loose soil. Others incrust them- 

 selves with a silky or glutinous matter, which they push out 

 from their mouths, without spinning it into threads. Others re- 

 tire into the holes of walls or of decayed trees. Others suspend 

 themselves to the twigs of trees, or to other elevated bodies, 

 with their heads undermost. Some attach themselves to walls, 

 with their heads higher than their bodies, but in various in- 

 clinations ; and others choose a horizontal position. Some 

 fix themselves by a gluten, and spin a rope round their middle, 

 to prevent them from falling. Those which feed upon trees 



