( cxxiv ) 



would be opposed to the views generally accepted that there 

 are variations that "do not count,"* or, to use Weismann's 

 term, are " biologically indifferent." f But there are many 

 species which exhibit variations that, so far from being triiles, 

 are of a very striking character, such as would challenge 

 selection if it took that direction. 



Striking differences in fades. 



Among these striking characters, the facies presented to 

 vision, including colour and design or pattern in conspicuous 

 markings, at once suggests itself as probably the most effective, 

 it being so extensively made use of for concealment and other 

 vital pvirposes. Its usefulness for any such purposes is of 

 course limited by the necessity for a sufficiency of light to 

 show it, and of suitable seeing capacity on the part of the in- 

 terested observer. Absolute darkness generally reduces insects 

 to quiescence, but absolute darkness is rare during the active life 

 of insects ; it is practically limited to the few hours out of the 

 twenty-four in which there is neither daylight, twilight, moon- 

 light nor starlight, and, in the higher latitudes, duinng the 

 summer months, when insects are most active, there is either 

 no night at all or a very brief one. Moreover, a large minority 

 of species of Lepidoptera are active in broad daylight only, 

 and of the remainder that are only active in obscurity, a very 

 large number are, while in a state of rest, fully exposed by day 

 to observation and consequent destruction, so that even to 

 human eyes, ill adapted as they are to pierce obscurity, the 

 colours and patterns of these insects are more or less conspicuous, 

 and may therefore be important characters, J 



* Thus Darwin speaks of "variations wliich are of no service or dis- 

 service to the species, and which consequently have not been seized on and 

 rendered definite by natural selection." — "Origin of Species," p. 55. We 

 are much too ignorant of the whole economy of any one organic being to 

 say what sliglit modiiications would be of importance or not. — Ih. p. 245. 

 (Organs in process of extinction disa]ipear so slowly that they must long be 

 cumbrous.) See also Mr. Bateson's observations on the excessive variation 

 of Coccinella decemjnindata side by side with the invariability of C. scptem- 

 •punctata, "Materials for the Study of Variation," pp. 572-3. 



t " Evolution Theory," vol. i (English translation), p. 54. 



:;: ^Many species of predaceous beetles, bugs and other carnivorous insects 

 hunt by night, and insects which, like butterflies, rest by night must be 

 much at their mercy ; moths that move about actively by night must have 

 better chances of escape from them. As to the seeing powers of inseets, 



