CLASS I. INSECTA: 
ORDER 4. LEPIDOPTERA. 
571 
these insects are due; and the metallic tints exhibited bj many species are owing to the pres- 
ence of very delicate stripes npon the scales. 
The larvae of the Lepidoptera are well-known as Caterpillars. These are generally more or 
less cylindrical, composed of thirteen segments, of which the anterior forms a horny head furnished 
with jaws and antennas, and usually with groups of simple eyes. The jaws are strong and well- 
adapted for "biting the fine vegetable tissues on which the most of them feed. 
The duration of the larva state is very variable in these insects ; many of them producing two 
broods annually, while others occupy two or three years in arriving at their perfect condition. In 
their larva state they arc exceedingly voracious, often doing immense damage to vegetation : 
most of them accordingly grow rapidly, and shed their skins several times before attaining maturity. 
AVhen this period has arrived, the caterpillar seeks some sheltered spot in which to undergo its 
change to the pupa form. Some species select the lower surface of leaves and branches for this 
purpose; others, clefts and hollow^s in the bark of trees, walls, or p_alings ; while others bary 
themselves in the earth. Those which remain in the air suspend themselves in various ways by 
means of their silky secretion, and some inclose themselves completely in a silky cocoon. This 
is also done by some of those which conceal themselves in the earth; but many of these only line 
their cavity with a sufficient quantity of silken threads to keep its walls from falling in upon them. 
The pupa is entirely inclosed in a horny case, in which the position of the wings and limbs is 
indicated, externally, only by lines and other elevations. 
In their preparatory stages the Lepidoptera are exceedingly liable to be destroyed by numerous 
species of parasitic insects, which lay their eggs in the larva; the latter still continues to feed, 
and frequently even effects its transformation to the pupa state, without exhibiting any indica- 
tions of the work of destruction which is going on within. These parasites, assisted by the insect- 
ivorous birds, keep the numbers of caterpillars within moderate limits. Without these checks 
they would soon destroy the fruit of the labors of the gardener and the husbandman.* 
THE SYBIL BUTTERFLY. 
The perfect insect, on first emerging from the pupa case, usually has the wings soft and 
crumpled ; and it is not until some little time after it has set itself free from its prison that its 
* There are said to be twelve hundred species of lepidopterous insects in this country, and the numbers of each are 
of course beyond computation. One female will produce three hundred eggs a year, and if her offspring were to go 
on at that rate of increase, in four years her progeny would be eight thousand one hundred millions. The necessity 
of powerful checks upon such prolific and voracious species is obvious. The birds are immense destroyers of cater- 
pillars. A single woodpecker will destroy fifty or sixty a day ; thus one million of woodpeckers, during the months 
of April, May, June, and July, will destroy six billions annually. 
