\rOMOLOGY. 



me: il doubtless the sense of smell lik< the 



night ti while during the day they trust to 



their ibly in some Cicadas also to hearing. 



study of the sensations of I1 at the same time 01 



the most difficult and one of the most interesting of the departments 

 ntomology. But as yet comparatively little has 

 done in this line. The great improvements that 

 have recently been made in the methods of histologic- 

 al research have resulted in the publication of several 

 important papers on the structure of sense-organs ; 

 but there is a great lack of experimental basis for con- 

 clusions as to the functions of the various organs that 



been described."" 



The best known of the organs of special sen 

 the organs of sight. Of these there are two kinds, 

 the simple eyes and the compound eyes. Simple 

 ist in both larvae and adult insects. In the 

 former there may be several of these, on each side of 

 the head ; in the latter there are usually not more 

 than three, situated between the compound 

 The compound eyes occur only in adult insects, where 

 they reach a marvellous degree of complexity. 

 compound eye consists of many ocelli united; the 

 number varies from 50 in some ants to more than 

 BJ V ^ 30,000 in certain butterflies. The complexity of these 



FIG. 45. - Three eyes docs not, however, consist merely of the great 



ocelli with retinu- , , ... . . , 



i from the com- number of ocelli that enter into the composition ot 



pound eye- . . . . . 



tie(After each; but each ocellus is a highly developed 



f MM 



ting of manv parts. 1 he .structure of these ocelli 



dissolved away . 



atly in different insects/*- H<r. i^ rcpre- 



j ~TJ 



nts three ocelli of a May-beetle as described by 



...mem- 

 heat Gi her. 



P' With regard to the organs of special .her 



"' than th" ight there is much doubt. It is prob- 



j of hearing ; for elaborate 

 common among tin in. Hut the only 



.1 general <: r many r- 



see / 



IV. (1886). 



t Ser , ions >f the Simple and Compound i 



sects ( i -78); also the * !,y this author. 



