Page:Insects - Their Ways and Means of Living.djvu/305

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The pllpa has so many of the characters of the mature insect that we lnight sa / it is self-evident that it is a part of the adult stage, except that to say anything is "se]f- evident" is almost an unpardonab]e remark in scientific writing. However, it is clear to the eve that the pupa, in casting off the skin of the ]arva, has'entirely discardcd the larva] for/n, except in certain insects t]at have a larva] form in the adult stage. The pupa llliiV rctain a few Ulfimportant ]arval characters, but all its principal organs are th-se of an adult insect in a ha]fway stage of development. In studying the cicada, it.was«fi»servcd that the adult issues from the skin of the nymph in a very immature condition. A carefid dissecti«m «f a specime at this rime would show that the creature is still imperfect in many wavs besides those which appear externallv. By very rapid rowth during the course (,f an hot/r, hoveve, the adult form and organs are perfected. We have also noted that with insects of incomplete metam-rphosis the adult is mostly formed within the nymphal skin some rime before thë latter is cast off. The same thing is true of a pupa. For several davs bel.re the caterpillar is ready to molt the last rime, i't remains ahnost motionless and "its Imdv contracts to perhaps less than hall of the original lenth. The caterpillar is now said to be in a "prepupal" stage, but examination of a specimen will reveal that it bas alread transfcrmed, f-r inside its skin is a sort pupa in a préliminary stage of development (l;ig. 4 B). This first stage of the pupa of a moth or butterfly (Fig. 41 B) is entirely comparable with the immature adult of the cicada fi»rmed inside the skin of the last stage of the nymph (Fig. 4  Al. The entire pupal period, therefore, corresponds with the formative stage of the cicada, which begins within the nymphal skin and is com- pleted about an hour after the emergence. The only external différence between the two cases is that the pupa sheds its skin, making a final added molt before it becomes

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