280 MENTAL EVOLUTION IN ANIMALS. 



when the moon is in the horizon ? I formerly observed that 

 they liy very much less at candles on a moon-light niglit. 

 Let a cloud pass over, and they are again attracted to the 

 candle." 



I do not know to whom this observation is due ; but I 

 quote it for the sake of the query. The answer, I think, 

 must be, that as the moon is a familiar object, the insects 

 regard it as a matter of course, and so have no desire to 

 examine it. I have little doubt that if moonlight were con- 

 centrated to a point in a dark room, the moths and gnats 

 would approach it. 



In " Nature " (vol. xxv, p. 436), Mr. J. S. Gardener 

 writes : — 



" Whilst watching the great horse-shoe falls of the Skjal- 

 fandafljot near Sjosavan in Iceland, I saw moth after moth 

 fly deliberately into the falling water and disappear. Some 

 which I noticed arriving from a distance, fluttered at first 

 deviously, but as they neared the water flew straight in. The 

 gleaming falls seemed at least as attractive as artificial 

 light." And doubtless the same explanation applies, inas- 

 much as a gleaming waterfall is not a sufficiently common 

 oliject in Nature, either to fail in arresting the curiosity of 

 the moths, or to ensure that a special instinct should be 

 developed to warn the insects from approaching it. 



3. Mr. Da^rwin in the Appendix points out two or three 

 cases of instinct which are apparently at first sight detri- 

 mental to the species exhibiting them. Thus, the crowing of 

 the cock-pheasant on going to roost reveals his presence to 

 the poacher, the cackling of a hen after having laid an egg 

 informs the natives of India where the nest is concealed, 

 certain birds place their nests in very conspicuous situations, 

 and a kind of Shrew-mouse betrays itself by screaming when 

 approached. Now it seems to me that in all these cases — 

 and many similar or analogous ones might be given — the 

 difficulty is, if I may use the term, fictitious ; for it only arises 

 when we shut our eyes to some of the most important prin- 

 ciples which in the previous chapters I have been endeavour- 

 ing to explain. These principles do not imply that an instinct 

 should ever be formed or modified with reference to a j^rospec- 

 tive change of environment, while they do imply that when 

 such a change has taken place, time must be allowed for 

 the compensating modification of the instinct — even suppos- 



