THE STUDY OF INSECT LIFE 9 



The antennae or horns on the upper surface 

 of the heads of insects are extremely variable 

 in their form, and offer many important 

 points in the identification and classification of 

 insects. They present considerable complexity 

 of structure, and are undoubtedly sensory 

 organs, though whether they are organs of 

 single sense or of a combination of senses 

 has not yet been clearly settled. It has been 

 most conclusively proved, however, that their 

 most important function is to act as organs 

 of touch. Between the minute, microscopic 

 " touch-hairs," which are very numerous on 

 the antennae, are to be found equally minute 

 depressions or cavities, each covered by a thin 

 layer bearing on its outer surface a series of 

 rings. Into the tiny cavity below each hollow 

 passes a nerve-end cell. Other important and 

 complex cavities are situated in small patches 

 at the lower parts of the joints of the antennae. 

 The exact function of these minute cavities is 

 still open to question, being considered by some 

 anatomists to be olfactory organs, while by 

 others they are thought to be auditory organs. 

 Insects have undoubtedly the sense of smell 

 well developed, and considering the large num- 

 ber which have the power of producing sounds, 

 we may also infer that the sense of hearing is 

 developed to a like degree; but the exact seat 

 of these two senses has not been at all clearly 

 and firmly established, although, from their 

 peculiar structure, the pits to be found on the 

 antennae may well be supposed to have some- 

 thing to do with the sense of smell or hearing. 



