LIFE IN SECONDARY TIMES 257 



been so beautifully observed and have inspired such eloquent 

 writing on the part of that great naturalist, the recluse of 

 Serignan, J. H. Fabre. 1 In those species which feed on sweet 

 liquids, whereas they nourish their young on animal prey, we 

 can even trace the transformation from a carnivorous diet, at 

 first common to larvae and adults, to a sugar diet, originally 

 limited to the adults as in various Wasps, and then extended 

 to the larvae as well, as in the case of Bees and Ants. It is 

 obvious then that instincts have been evolved, though any 

 explanation of such evolution is brought up against a difficulty 

 which seemed insurmountable to Darwin, Romanes, and 

 myself, which set Fabre against the doctrine of evolution, and 

 whose solution I myself only guessed at much later. 2 This 

 explanation lies simply in the fact that the Hymenoptera, 

 among all insects able to live on liquid food, are those in whom 

 the mouth-parts have the most varied aptitude, so much so 

 that we find among them all the transitional stages between a 

 mouth adapted almost entirely for crushing and one essen- 

 tially constructed for licking, so to speak, like that of the Bee. 

 Hence they were able to profit more greatly than the Lepidop- 

 tera and Diptera by the particularly favourable conditions 

 prevailing in the calm, warm Secondary Period. The advent 

 of winter seasons caused the disappearance of all those insects 

 wliose individual evolution took longer than a year, and which 

 had not learned to shelter their larvae or themselves against 

 the rigours of the periodic cold season. Among those indi- 

 viduals whose evolution took less than a year, only those 

 survived whose development happened to take place during 

 the summer. In this way the seasonal rhythm of Insect 

 reproduction became established. This rhythm had as a 

 result the isolation of one generation from another. While 

 the brevity of life cut out experience, the seasonal rhythm did 

 away with education. The insect brain, however, was already 

 sufficiently organized to make most of the reproductive acts 

 automatic. Heredity preserved what has been acquired in this 

 way, but the winters prevented all possibility of modifications, 

 and in this way the instincts that had become fixed took on 

 that guise of mystery that deterred for so long any attempt at 

 explanation. As soon as the veil of mystery is withdrawn, we 

 arrive at the apparent paradox that the very fixity of Insect 



1 LXXVII. 2 LXXVIII. 



