The Senses of Animals. 



259 



into a locality frequented by these moths, he will soon be 

 surrounded by twenty or thirty males; but if the moth 

 be not a virgin, he will at most see one or two males. 

 The sense of smell is thus delicate enough to distinguish 

 the fertilized from the unfertilized female, and has asso- 

 ciated with it a sense of direction by which the insect is 

 guided to the right spot. Carrion flies whose antennae 

 have been removed fail to discover putrid flesh; and E. 

 Hasse has observed that male humble-bees whose antennae 

 have been removed cannot discover the females. The 

 sensory elements are lodged in pits or cones, which may be 

 filled with liquid, peculiar sensory rods or hairs being 

 associated with the nerve-end- 

 ings. Of these pits the queen- 

 bee has, according to Mr. 

 Cheshire, 1600, the worker 2400, 

 and the drone nearly 19,000, on 

 each antennae. On the antennae 

 of the male cockchafer, Hauser 

 estimates the number to be 

 39,000. 



In the aquatic crayfish there 

 are, besides the long antennae, 

 smaller antennules, each of 

 which has two filaments, an 

 inner and an outer. On the 

 under surface of most of the 

 joints of the outer filament 

 there are two bunches of 

 minute, curiously flattened or- 

 gans, which were regarded by 



T T ,1 . T '^■0-y inner joint; o.j., outer joint; o?., 



Leydlff, their discoverer, as olfactory sette; ol., the same, enlarged; 



^„ . -. T . au.op., auditory opening in the basal di- 



oliactory. Observation, too, ^*^^"°' ^^^^^ ^^^ ^^^° '^^^ open to show 



•^ ' au.s., the auditory sac; au.n., auditory 



seems to confirm the view that "^'■^®^^'*"^^""s*o*'^^*^°"'^ses beset with 



""" auditory hairs ; au.h., auditory hau: ea- 



the sense of smell (or tel^es- ^*'^^^- ^^"^^ Howes.) 

 thetic taste) is located in the antennule. I tried on a 

 crayfish the following experiment : When it was at rest 

 at the bottom of its tank, I allowed a current of pure 



Fig. 26.— Antennule of crayfish. 



