STRUCTURE AND CLASSIFICATION. 



43 



imagine the sort of picture an insect perceives, and we are by no 

 means certain how well or how poorly it really does see. We know 

 only that larval forms and low types, provided with ocelli only, 

 see very feebly and indefinitely, and can do little more than dis- 

 criminate between light and darkness. Many insects have no eyes 

 at all, living under such circumstances as to make them useless. 



That insects hear follows almost inevitably from the fact that 

 many of them "sing," — that is, produce some sort of noise. 

 What those organs of hearing are is not so certain in all cases, 

 nor where they are situated, since we cannot confine our search 

 for ears to the head alone. In the Orthoptera they have been 

 located with a reasonable degree of certainty : in the grasshopper 

 the ears are on each side of the basal segment of the abdomen, 

 while in the locusts and crickets they are on the anterior tibiae. 

 Essentially, these ears consist of a tense membrane stretched over 

 a cavity, and connected by means of little processes, correspond- 

 ing somewhat to the bones of the human ear, with a bulb-like 

 vesicle and a large auditory nerve. In most other orders no 

 similar structures are found, and the sense of hearing is located 

 in the antennae, or feelers, of which more will be said later on. 



Insects are able to discriminate as between foods, and the sense 

 of taste is undoubtedly developed to some extent ; but the taste 

 which seems agreeable to their sense would be to us, in many 

 instances, the vilest conceivable. No true tongue, as this organ 

 exists in the vertebrates, is found among insects ; but on the up- 

 per side of the lower lip there is often a finely papillate surface, set 

 with little fleshy pegs and processes communicating with nerve 

 fibres, and this represents the nearest approach to the tongue 

 of the higher animals. It is called the hypopharyyix , and is 

 not always present. Beneath the labrum, or upper lip, we often 

 find a separate, flat, similar piece, and this is the epipharynx^ 

 corresponding in function to the palate of the higher animals. 



Nothing resembling a nose is found among insects, and yet 

 the sense of smell seems very highly developed. Insects often 

 discover their food with unerring certainty, even when concealed 

 from sight. Among the nocturnal species, where sight can play 

 but a small part at best, the sense of smell seems most highly 

 developed, and usually more in the male than in the female. 

 This is due to the fact that the males, as a rule, seek their mates. 



