

METAMOEPHOSES OF MUSCID^ AND LEPIDOPTEEA. 347 



as amongst all other insects, speedily dies after the impregnation of the 

 female has been effected ; but the female from this period begins to 

 swell enormously from the development of her countless eggs, and by 

 the time she is ready to commence laying, her abdomen is about 1500 or 

 2000 times larger than all the rest of her body (fig. 174, E). During the 

 period of this swelling, the workers remove the walls of the royal apart- 

 ment, uniting the nearest cells to it ; so that in proportion to the increase 

 of the body of the queen, the size of the abode she inhabits is also in- 

 creased. She now commences laying eggs, and during the process the 

 abdomen exhibits a continual undulatory motion, produced by the peri- 

 staltic movement of the egg-ducts ; while the workers convey away the 

 eggs as they are laid, and deposit them in the distant rearing- cells of 

 their wonderful habitation. The reader will be able to form some idea of 

 the relative proportions and outward appearance of the edifices erected by 

 these comparatively minute beings by the group of their citadels repre- 

 sented in the background of the figure; but to describe them more 

 minutely would lead us into details unconnected with our subject*. 



(906.) The eggs of these little animals vary much in shape and ex- 

 ternal configuration ; so that, from the beauty of their forms and exqui- 

 site sculpture, some of them are interesting objects for the microscope. 



(907.) We have already spoken concerning the metamorphoses which 

 insects undergo during the progress of their development from the form 

 under which they first leave the egg to their mature condition, when 

 they become fertile, and, in most instances, acquire those instruments of 

 flight so generally characteristic of their perfect state. Before entering 

 upon a more minute inquiry concerning the physiological principles 

 upon which the important changes in question depend, and the pheno- 

 mena attending the process, it will be advisable to cite a few more 

 examples illustrative of the most interesting varieties of metamorphosis 

 signalized by authors. Fabricius distinguishes five different kinds of 

 metamorphosis, and has applied a different name to each. 



(908.) The first class comprises all insects of which the larva is a 

 maggot entirely deprived of legs, that, after having changed its skin, or 

 moulted, a certain number of times, becomes, previous to its last change, 

 encased in an oval horny sheath, or pupa-case, whereon not the least 

 trace of the limbs of the mature insect is to be detected. Such pupaB are 

 absolutely without the power of motion, and are distinguished by the 

 name of coarctate. Examples of this sort of metamorphosis are met with 

 in the common House-flies (Muscidce); and the forms of their larvae and 

 pupao are familiar to every one. 



(909.) Of the second kind, technically named obtected, the Lepidoptera 

 furnish well-known instances. The changes which occur in the deve- 

 lopment of the Silkworm, represented in the annexed figure (fig. 175), 

 may readily be witnessed. In such insects the full-grown caterpillar, 

 * Vide Smeathman, Phil. Trans, vol. Ixxi. 1781. 



