INSECTA. 581 



nnteiJite. The metamorphoses which all undergo, hefore 

 they arrive at the perfect state and are ahle to fulfil all 

 the ends of their existence, are more curious and striking 

 than in any other department of nature ; and in the 

 greater number of species the same individual differs so 

 materially at the several periods of life, both in its in- 

 ternal and external conformation, in its habits, locality, 

 and kind of food, that it becomes one of the most inter- 

 esting investigations of the physiologist to ascertain the 

 manner in which these changes are effected, to trace the 

 successive steps by which that despised and almost un- 

 noticed larva that but a few days before lay grovelling in 

 the earth, with an internal organization fitted only for 

 the reception and assimilation of the crudest vegetable 

 matter, has had the whole of its external form so com- 

 pletely changed, as now to have become an object of 

 admiration and delight, and able to "spurn the dull 

 earth," and wing its way into the wide expanse of air, 

 with internal parts adapted only for the reception of the 

 purest and most concentrated aliment, which is now ren- 

 dered absolutely necessary for its support, and the reno- 

 vation increased energies demand. 



The greater number of insects undergo a complete series 

 of changes. They are for the most part oviparous, and 

 their eggs assume a variety of forms, colour, &c. as 

 will be seen in Plate VI. On first leaving the egg, they 

 assume a more or less worm-like appearance, known as 

 larva, maggot, or caterpillar. The next stage is that of 

 the nympha, pupa, or chrysalis ; this is succeeded by that 

 of the perfect insect or imago. In some insects the 

 changes are incomplete; the body, legs, and antennas 

 are nearly similar, but wings are wanting. In others the 

 pupa continues active, is of a large size, and acquires 

 rudimentary wings ; and some are without material altera- 

 tion of structure, the change consisting in what is termed 

 " icdysis," a casting off, or moulting only. 



The heads of insects present many points of interest; 

 Plate VI. No. 134, shows the head of the Tortoise butter- 

 fly in profile, with large compound eye, palpi, and spiral 

 tongue. No. 131 is a portion of the head with lancets, 

 &c. of the Glossina morsitans, Tsetse-fly of Africa. In 



