STRUCTURE OF INSECTS. 



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larger than it is in the larva state. Its integument, 

 which, from analogy with vertebrated animals, has 

 been called the skull, or cranium, (c, Fig. l.'iO), is 



usually the hardest part of the general crust. 

 Although it may appear, on a superficial examina- 

 tion, to consist of a single undivided piece, yet, on 

 tracing its gradual formation, it is found to be in 

 reality composed of several of the segments of the 

 larva united together. Audouin and Cams dis- 



