JANUARY. 



maxilla, by which they gnaw their food ; and HAUSTELLATA, 

 where these jaws are replaced by minute laminae forming a 

 kind of sucker, haustellum, which is received into a sheath, 

 the insects of this class procure their food by suction, 

 either from animal or vegetable substances. The other parts 

 of the mouth are the palpi, or feelers, small moveable ap- 

 pendages placed on each side, which vary in size and num- 

 ber ; the promuscis or rostrum being the part forming the 

 mouth in many of the sucking insects; the proboscis, or 

 sheath, which contains the trophi, or organs of the mouth 

 in Dipterous insects ; and the antlia, or suckers, the organs 

 constituting the principal part of the mouth in Lepidoptera. 

 This organ is generally very slender ; in the family Sphingida 

 it is long, in Papilionida much shorter ; in a state of rest 

 it is rolled spirally between the palpi. 



The eyes of insects are of two kinds, simple and com- 

 pound, horny, immoveable, and unprotected by any eyelid. 

 When closely examined, they are found to consist of a great 

 number of minute hexagonal lenses, each of which forms a 

 distinct organ of vision ; of these, the common Ply possesses 

 4000, the Silk-worm Moth 6236, and some Butterflies 

 17,355 : when detached from the head and cleaned, they 

 are found to be as clear as crystal. The celebrated naturalist 



