108 INSECTS. 



channels. Thus, the two jointed members called 

 antennae, that project from the head, are believed by 

 some to be organs of touch ; by others, to convey 

 delicate perceptions unknown to us ; and by the 

 generality of entomologists are considered to be in 

 some way sensible to sound. They are composed of 

 a varying number of rings, sometimes as many as 

 thirty, set in succession; the whole constituting a 

 tube, and enclosing nerves, muscles, and air-pipes. 

 Their form is exceedingly varied ; and in many in- 

 stances they are ornamented with feather-like beards, 

 or curiously sculptured, so that they afford useful 

 characters for the identification of the multitudinous 

 genera comprised in this Class. 



The eyes of insects present some interesting pecu- 

 liarities of structure, indicative, no doubt, of corre- 

 sponding diversities in the sense of vision, of which 

 we must ever remain ignorant. Two distinct kinds 

 of eyes are possessed by these animals, both kinds 

 being present in the majority of species. If we 



\ examine the head of a bee, for 



.#>. f example, we find a large con- 

 ,^r:mo0 vexity on each side, whicn a mag- 



^_^: ~ nifying glass discovers to be coni- 



-^^' posed of an immense number of 



I facets, and on the summit of the 

 / head, between these, we see three 

 shining points, resembling minute 

 ' " ' gems, set in a triangular form. 



Fig. 73.— eyes of bee. The former are termed compound, 

 the latter simple eyes. The simple eyes consist ol 

 a glassy lens, behind which a nervous thread is spread 

 out, forming a retina, or net-work, as in the higher 

 animals, to receive impressions of sight. The struc- 

 ture of these eyes is sufficiently intelligible, but our 

 admiration is greatly excited when we come to con- 

 sider the large convex organs of compound vision, 

 and find that each of these contains many thousands 

 of eyes, all capable of distinct perception. The 

 microscope reveals to us that the compound eye of 



