12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



posed at ecdysis when the larval skin is shed. The young pupa still 

 enclosed in the larval cuticle has, therefore, been more properly 

 named by Hinton (1958) the pharate pupa (from the Greek word 

 for hidden or concealed). The same term would apply to any larval 

 stage still cloaked in the skin of the preceding instar, and to the adult 

 when it is still cloaked in the pupal skin. Among the muscoid flies, 

 the larva completes its growth, changes to the pupa, and finally to 

 the adult, all inside the cuticle of the third larval instar. The cuticle 

 of the third larval instar becomes greatly modified during this time 

 and it is termed the puparium after this modification; from the 

 puparium the fully formed adult emerges. 



Metamorphosis: The term is derived from the Greek words 

 meta, a change, + morphe, form, + osis, a process of. Following 

 its derivation the term metamorphosis means literally "a process of 

 changing form," and it should be emphasized that the implied change 

 is one of form and not of substance. Thus it is comparable to the 

 change of water to ice, not to the replacement of ice crystals by salt 

 crystals or something else. The term, however, is widely used in 

 zoology for almost any conspicuous change of form that an animal 

 makes during its development regardless of how this is done. The 

 tadpole is said to metamorphose into a frog, but it does so by a con- 

 tinuous changing growth; and if this is metamorphosis then so is 

 the embryonic development of any animal. The term probably origi- 

 nated with the early writers of fiction who were fond of inventing 

 tales about human beings who, at the whim of some offended god or 

 goddess, were transformed into other animals or trees. It is, of course, 

 to be supposed that in such imaginary cases the flesh and bones of 

 the human were directly transformed into those of the animal. The 

 early naturalists took over the word metamorphosis and applied it to 

 the seemingly similar transformations of insects such as that of a 

 caterpillar into a butterfly at a time when it was perhaps not known 

 that the caterpillar was simply a young butterfly. Once established, 

 the word metamorphosis became a standard part of our entomological 

 nomenclature well before the true nature of the change from larva 

 to adult was known. 



Modern studies on insect "metamorphosis" show that most of the 

 larval tissues disintegrate and that the adult tissues and organs are 

 newly built up in the pupa from cells that never formed an integral 

 part of the larva. The adult cuticle is always a new secretion from 

 the epidermal cells, which themselves may not change, though in some 

 insects the larval epidermis itself is destroyed and replaced by an 



