38 EUeii — rreddeiitlal Address. 



tUid experiment, iiiul di-aw conclusions from well uttested results.- 

 Sight. — Taking lirst the sense of sight, mucli has l)een written 

 as to the i)ictnre which the compound eye of insects produces 

 iijjon the hi'ain or upon the nerve centers. Most insects which 

 undergo complete metamorphoses possess in their adolescent states 

 simple eyes or ocelli, and sometimes groups of them of varying size 

 and in varying situations. It is difficult, if not impossible, to 

 demonsti'ate experimentally their efficiency as organs of sight ; 

 the i)rol)abilities are that they give but the faintest impressions, 

 but otherwise act as do our own. The fact that they ai'e pos- 

 sessed only by larv;y which are exposed more or less fully to the 

 light, while those larvf>f which are endophytous, or otherwise hid- 

 den from light, generally lack them, is in itself proof that they 

 perform the ordinary functions of sight, however low in degree. 

 In the imago state the great majority of insects have their sim])le 

 eyes in addition to the compound eyes. In many cases, however, 

 the former are more or less covered with vestiture, vvhicli is an- 

 other evidence that their function is of a low order, and lends 

 weight to the view that they are useful chiefly for near vision 

 and in dark places. The compound eyes are prominent and ad- 

 justable in pi'o})ortion as they are of service to the species, as wit- 

 ness those of the common House-fly and of the Libellulid;^ or 

 Dragon-flies. It is obvious from the structure of these com- 

 pound eyes that impressions through them must be very differ- 

 ent from those received through our own, and, in point of fact, 

 the late experimental researches of Hickson, Plateau, Tocke and 

 Lemmermann, Pankrath, Exner and Viallanes, practically estab- 

 lish the fact that while insects are short-sighted and perceive 

 stationary objects imperfectly, yet their compound eyes are better 

 fitted than the vertebrate eye for apprehending objects set in re- 

 lief or in motion, and are likewise keenly sensitive to color. 



So far as experiments have gone, they show that insects have 

 a keen color sense, though here agnin their sensations of color 

 are different from those produced upon ns. Thus, as Lubbock 

 has shown, ants are very sensitive to the ultra violet rays of the 

 spectrum, which we cannot perceive, though he was led to con- 

 clude that to the ant the general aspect of nature is presented in 

 an aspect very different from that in which it appears to ns. In 

 reference to bees, the experiments of the same author prove 

 clearly tliat they have this sense of color highly developed, as 



