84 TRUE TALES OF THE INSECTS. 



experimental basis for conclusions as to the functions of 

 the various organs described. However, there is a great 

 variation in the degree of perfection of the different 

 senses in different insects. 



The sense of sight must be well developed in the 

 Acridiidae, for they are furnished with two large well- 

 developed compound eyes, and three simple ones (ocelli), 

 supplied with nerves of special sense. The compound 

 eyes are situate at the sides of the head ; in front are the 

 ocelli, one on each side between the eye and the insertion 

 of the antenna ; the third ocellus being in the middle, 

 immediately in front of the base of the antennae. This 

 family is one of the large groups of insects in which the 

 coexistence of the two kinds of eyes is most constant. 

 The ocelli, however, vary much in their development, 

 being in some cases prominent and easily perceived, 

 while in others they are very imperfect, difficult to 

 detect, apparently functionally useless. In what way 

 the insects specially need two sorts of eyes, is not clear. 

 Later on we shall see that a similar condition in regard 

 to sensitiveness to sound is believed to exist in this 

 family. The antennae are organs of touch ; and the palpi 

 not only serve the same function, but probably are 

 endowed with the sense of taste. 



It need hardly be said an insect breathes by means of 

 a complicated system of air-tubes or tracheae, ramifying 

 through every part of its structure, and communicating 



