174 SOCIAL LIFE IN THE INSECT WORLD 



Moreover — a matter of still greater importance — the 

 larvae of the Osmia fed in this manner attain their 

 normal growth and spin their cocoons, from which 

 adults issue in the following year. Despite the albu- 

 minous diet the cycle of evolution completes itself 

 without mishap. 



What are we to conclude from all this ? I confess I 

 am embarrassed. Omne vivum ex ovo, says the physio- 

 logist. All animals are carnivorous in their first begin- 

 nings ; they are formed and nourished at the expense of 

 the egg, in v/hich albumen predominates. The highest, 

 the mammals, adhere to this diet for a considerable 

 time ; they live by the maternal milk, rich in casein, 

 another isomer of albumen. The gramnivorous nestling 

 is fed first upon worms and grubs, which are best 

 adapted to the delicacy of its stomach ; many newly 

 born creatures among the lower orders, being imme- 

 diately left to their own devices, live on animal diet. 

 In this way the original method of alimentation is 

 continued — the method which builds flesh out of flesh 

 and makes blood out of blood with no chemical pro- 

 cesses but those of simple reconstruction. In maturity, 

 when the stomach is more robust, a vegetable diet may 

 be adopted, involving a more complex chemistry, 

 although the food itself is more easily obtained. To 

 milk succeeds fodder ; to the worm, seeds and grain ; to 

 the dead or paralysed insects of the natal burrow, the 

 nectar of flowers. 



Here is a partial explanation of the double system 

 of the Hymenoptera with their carnivorous larvae — the 

 system of dead or paralysed insects followed by honey. 

 But here the point of interrogation, already encountered 



