SPECIAL PRECAUTIONARY HABITS 323 



natingly nocturnal, this habit, though perhaps partly protective, 

 is primarily due to the fact that a large amount of moisture is 

 essential to these creatures, for any great amount of evaporation 

 from their skin (which helps in breathing) would be deleterious, 

 if not fatal. Large eyes are often possessed by them, and the 

 Flying Frog (species of Rhacophorus) are particularly well en- 

 dowed in this respect. 



Many Fishes are of nocturnal habit, and there can be little 

 doubt that in some cases protection is one of the ends thus 

 attained. But, precisely as in land -vertebrates, the value of 

 this arrangement is much reduced by the fact that predaceous 

 forms may have the same habit. As fishes commonly discover 

 their food by means of touch and smell, darkness is not the 

 same hindrance to feeding that might be anticipated. 



Many Invertebrates are nocturnal, but our knowledge of their 

 habits is too scanty in most cases to permit of more than some- 

 what vague conjecture. It is highly probable, however, that the 

 practice of feeding at night exemplified by such insects as Cock- 

 roaches, Crickets, and Moths acts more or less as a protection. 

 Nor is it impossible that this may be one of the ends served by 

 the phosphorescence of certain insects. This phenomenon is 

 perhaps most strikingly seen among the Fire- Flies, which con- 

 stitute a family {Lainpyridce) of tropical beetles. 



Many marine invertebrates, belonging to widely -differing 

 groups, are more active by night than day. Hosts of creatures 

 which during the latter are submerged to some depth rise to 

 the surface when the sun goes down, especially when the weather 

 is calm. It is not known how far this habit has to do with pro- 

 tection, nor is the use of the phosphorescence characteristic of 

 many such forms fully understood. 



We have now seen that certain animals gain a measure of 

 protection from their foes by feeding during the night, but as the 

 same end is attained in other cases by feeding during the day, 

 it may be in such a way as to court rather than avoid observa- 

 tion. Space forbids the mention of more than a few typical 

 instances. 



FEEDING AT FAVOURABLE TIMES— DIURNAL ANIMALS 



Many herbivorous animals possessed of rapid means of pro- 

 gression, and endowed with keen senses by which the approach 



