28 INSECTS. 



as in the larva of Dyticus, a large water beetle, which 

 has five or six on each side, they are still simple, being 

 independent of each other, and having separate optic 

 nerves, whereas in compound eyes one large optic nerve 

 or ganglion sends branches to all the eyelets.* 



The antennae of insects have long perplexed naturalists, 

 who have in turn ascribed to them every known sense 

 but that of sight smell, touch, taste, even hearing. 

 It is not, however, even yet ascertained to what sense 

 they belong. They are evidently of the greatest impor- 

 tance to the insect in a variety of ways, aiding it in its 

 perceptions and guiding it in its actions, and this in 

 matters so various as to suggest that it may be the organ 

 of some sense or senses to which we have nothing corre- 

 sponding, or of the combination of which, at least, our 

 limited experience gives us no means of forming an idea. 



The forms of antenn to be observed are very various, 

 and, in some instances, exceedingly beautiful. Some 

 are thread-like, others clubbed, and others feathered- 

 all these are found in moths and butterflies : others 

 again are like strings of beads, or are toothed like a comb, 

 or terminate in a fan, as may be seen in beetles. In one 

 species of these last the antenna is about four times as 

 long as the body, while in certain species of flies it con- 

 sists principally of a little globe, with a curved bristle 

 sticking out of it, like the reaping-hook by which Daniel 

 O'Rourke held on to the moon. 



These organs are so valuable in the determination of 

 genera, &c., that the young student should from the begin- 



* These simple eyes are found in the spiders, woodlice, centipedes, 

 &c. ; none but the true insects (i.e., those which undergo metamorphosis) 

 possessing the compound eyes. 



