IMAGO STATE. 225 



had a specimen of Bombyx menthrastri, and six of Ophion 

 mnul(K, hatched from the pupae of Bombyx vinulus, which is 

 certainly a curious fact." I should presume from this state- 

 ment, which is, however, sufficiently destitute of precision, that 

 these various specimens were produced from a single pupa of 

 the puss-moth. On throwing off the pupa covering, the ar- 

 rival at the perfect state is ordinarily completed ; but a re- 

 markable exception to this' occurs in the Ephemera, which, 

 after flying about a short time with the wings fully expanded, 

 throw off another skin. The occurrence of a subsequent 

 moulting in this group does not, however, seem to warrant the 

 conclusion, that the preceding state is not that of the pupa, 

 nor to overthrow the opinion that the pupa state ought not 

 to be regarded as a distinct one. I apprehend, indeed, 

 that as the Lepidoptera and the dragon-flies are known to 

 shed a similar pellicle, its existence throughout the winged 

 insects ought, from analogy, to be presumed, until direct ob- 

 servation proves the contrary. 



SECTION III. 



THE GENERAL STRUCTURE OF INSECTS AS ESPECIALLY EXHIBITED 

 IN THEIR PERFECT STATE. 



Our attention must now be directed to the final and per- 

 fect state of insects, and in the first place to their structural 

 peculiarities. This branch of the subject will naturally divide 

 itself into two branches : first, the anatomy of the external 

 parts of the body ; and secondly, that of the internal organs. 



1. External Anatomy. 



Insects being animals destitute of any interior skele- 

 ton, it is necessary that their external covering should 

 be much thickened, and rendered sufficiently strong to give 

 support to the numerous muscles which are internally 

 attached to it. Hence, in the majority of insects, this 



