SOME OF THE "LOWER ORDERS" 199 



be brooded and young to be fed. In the second, the 

 males, as has just been remarked, must search for the 

 females, often indeed, in the case of many Moths, because 

 they are wingless. 



This search is conducted by the sense of smell. This 

 fact, familiar enough to-day to the entomologist and 

 the student of Evolution, was unknown to the earlier 

 naturalists. Neither Darwin nor Wallace suspected it. 

 It would have been wonderful if they had, for there is 

 nothing in the general appearance of these insects 

 which suggests an organ of smell, nor is there any- 

 thing in the structure of the nervous system which 

 would indicate this subtle sense. During recent years, 

 however, the number of workers engaged on the investi- 

 gation of the senses of animals has increased immensely, 

 and great strides have been made in perfecting instruments 

 of research. To the efforts of these workers we owe the 

 discovery of the seat of the scent-detecting organs and 

 the source of the scent. The former are furnished by 

 the antennae, which lodge also the senses of taste and 

 touch. 



Among the Lepidoptera these constitute important 

 secondary sexual characters, the antennae, among the 

 Moths at any rate, presenting striking differences in male 

 and female. The scent-producing organs are very elusive 

 structures, and so far have been definitely traced, among 

 Butterflies, only in the males, where they are formed 

 by certain peculiarly modified scales known as " andro- 

 conia." They may be either irregularly scattered over 

 the wing, or may form complex structures. Sometimes 

 they are arranged in the form of brightly-coloured, 

 bristle-like tufts on the hind-wings, sometimes in a fringe 

 along the edge of the hind-wing. In some of the Moths 



