of animal, silky, and excremental particles; this forms the state of the growing caterpillar: in the next stage it is composed of animal and silky particles; it is then the mature caterpillar: and lastly, it is reduced to the animal particles alone; and is termed in this state the chrysalis. The poet Cowper, in the following lines, beautifully illustrates this subject:
The beams of April, ere it goes,
A worm, scarce visible, disclose;
All winter long content to dwell
The tenant of his native shell.
The same prolific season gives
The sustenance by which he lives,
The mulberry leaf, a simple store,
That serves him—till he needs no more!
For, his dimensions once complete,
Thenceforth none ever sees him eat;
Though till his growing time be past
Scarce ever is he seen to fast.
That hour arrived, his work begins.
He spins and weaves, and weaves and spins;
Till circle upon circle, wound
Careless around him and around,
Conceals him with a veil though slight,
Impervious to the keenest sight.
Thus self-inclosed, as in a cask,
At length he finishes his task:
And, though a worm when he was lost,
Or caterpillar at the most,
When next we see him, wings he wears,
And in papilio pomp appears;
Becomes oviparous; supplies
With future worms and future flies
The next ensuing year—and dies!
Well were it for the world if all
Who creep about this earthly ball,
Though shorter-lived than most he be,
Were useful in their kind as he.
It has been already noticed that the progressions of the insects are accelerated by an increase of temperature; and some variation will equally be experienced where different modes of treatment are followed; and, in particular, where different periods of the year are chosen in which to produce and rear the worm. Malpighius, in his "Anatomy of the Silk-worm," says,
