SIMPLE AND COMPOUND EYES. 343 



The first thing we learn about them is, that 

 some insects possess what are called simple eyes, 

 and compound eyes. The accompanying cut re- 

 presents in part the head of a flea, 

 and is annexed in order to give a 

 specimen of a simple eye. The 

 little circle represents the position 

 of the simple eye. All the organs connected with 

 the head are supposed to be cut off. The head of 

 the bee on the preceding page furnishes us with 

 an excellent illustration of a compound eye. All 

 perfect insects are provided with compound eyes, 

 and a large number with simple eyes too; but 

 no imago or perfect insect has simple eyes alone. 

 We see, therefore, that the simple eyes are only 

 additional or supplementary organs to the com- 

 pound eyes, which are the chief organs of sight 

 in these creatures. These simple eyes are mi- 

 nute lenses generally placed upon the crown of 

 the head, or the forehead ; in the bee this is 

 their position; and by means of a pocket- glass, 

 they can be readily seen in this insect, by 

 looking at its head from above. They will be 

 found arranged in a triangular form. Sometimes 

 an insect is furnished with as many as sixteen 



