CLASSIFICATION OF INSECTS. 291 



both in their outward form and internal structure, which constitute what 

 is generally termed their metamorphosis. When this is complete, as for 

 example in the Butterfly, the insect, after leaving the egg, passes through 

 two distinct states of existence before it arrives at maturity and assumes 

 its perfect form. The female butterfly lays eggs which, when hatched, 

 produce, not butterflies, but caterpillars animals with elongated worm- 

 like bodies divided into numerous segments, and covered with a soft 

 coriaceous integument (fig. 143, A). The head of the caterpillar is pro- 

 vided with horny jaws and several minute eyes : the legs are very short, 

 six of them, which are attached to the anterior rings, being horny and 

 pointed, while the rest, of variable number, appended to the posterior 

 part of the body, are soft and membranous. The caterpillars, or larvae*, 

 live for some time in this condition, and frequently change their skin 

 as they increase in size, until at length, the last skin of the larva being 

 thrown off, the animal presents itself in quite a different form, enveloped 

 in an oblong case, without any external limbs, and almost incapable of 

 the slightest motion resembling rather a dead substance than a living 

 creature ; it is then called a chrysalis, nymph, or pupa ^ (fig. 148, B). 



(753.) On examining attentively the external surface of this pupa, 

 we may discern, in relief, indications of the parts of the Butterfly con- 

 cealed beneath it, but in a rudimentary condition. After some time 

 the skin of the pupa bursts, and the imago, or perfect insect, issues forth, 

 moist and soft, with its wings wet and crumpled ; but in a few minutes 

 the body dries, the wings expand and become stiff, and, from being a 

 crawler upon the ground, the creature is converted into a gay and active 

 denizen of the air (fig. 148, c). 



(754.) Such is the progress of the metamorphosis when complete ; but 

 all insects do not exhibit the same phenomena. Those genera which, in 

 their mature condition, have no wings, escape from the egg under nearly 

 the same form as they will keep through life ; these form the Insecta 

 Ametabolat of authors: and even among those tribes which, when 

 perfect, possess instruments of flight, the larva frequently differs from 

 the complete insect only from its wanting wings, and the pupa is re- 

 cognizable by being possessed of these organs in an undeveloped or 

 rudimentary state : an example of this is seen in the House-cricket 

 (fig. 145), in which A represents the imago ; B, the pupa ; c, the full- 

 grown larva ; D, the young just hatched ; and E, the eggs. 



(755.) The extensive class of INSECTS has been variously arranged by 

 different entomologists, and distributed into numerous orders . Among 



* So called, by Linnaeus, because in this condition the perfect form of the insect is 

 concealed as it were under a mask. Larva, Lat., a mask. 



f The first two of these names are purely fanciful : the last is derived from pupa, 

 a baby wrapped up in swaddling bands. 



| d, without ; fierajSoXij, change. 



The classification of Insects here given is that of Burmeister, which we select 



u2 



