102 INTRODUCTION TO ZOOLOGY. 



lively at tins period of their lives as at any other, and differ 

 in appearance from the perfect insect only in the absence of 

 wings. 



There is something in the contemplation of these changes 

 highly suggestive of poetic thought. The Caterpillar is seen 

 crawling on the earth, then apparently lifeless in its self- 

 constructed sepulchre, then flinging off the vestments of the 

 tomb, and, with beauty of form and powers unknown before, 

 entering on the enjoyment of a new state of existence. Hence 

 k is not surprising that the ancients found, in its transforma- 

 tions, a symbol of the vague and shadowy ideas they enter- 

 tained of the life of man here, of his repose in the tomb, and 

 of the probability of a more glorious state of being hereafter. 

 " Psyche," says an ingenious and learned writer, "means, in 

 Greek, the human soul, and it means also a Butterfly; of 

 which apparently strange double sense the undoubted reason 

 is, that the Butterfly was a very ancient symbol of the soul."* 

 A number of terms have been employed by entomologists 

 to denote the variety observable in insect metamorphoses: 

 but a better acquaintance with the laws observable in the 

 development of animals in their several stages, and a more 

 accurate acquaintance with the functions performed by differ- 

 ent organs and tissues in the animal frame, have stripped these 

 changes of much of their distinctive character. Some insects 

 are not, at any time, possessed of wings ; but up to the period 

 at which wings are developed, it is found that all insects 

 undergo a similar series of changes. In some, however, an 

 amount of change is undergone, before their liberation from 

 the egg, which others do not experience until they have been 

 some time in the enjoyment of active existence. The duration 

 of the several progressive stages of growth differs widely in 

 the several tribes; and this also tended to give to each an 

 apparently distinctive character, to which it was not in reality 

 entitled.! 



With regard to their food, insects may be said to be omni- 

 vorous ; for there is no animal or vegetable substance which 

 does not form the aliment of one or more species. Some live 

 entirely on putrifying substances, and, by thus removing them, 

 prevent the salubrity of our atmosphere from being impaired ; 

 others are rapacious, and subsist by the destruction of those 



* Nare's Essays, i. 107. Quoted by Kirby and Spence, iv. 74. 

 t Owen's Lectures, pages 236, 237. 



