120 DISCOVERY OH. 



believe that honey-bees, hornets and wasps originate 

 in putrescent matter upon which those other flies 

 occur." 



Towards the end of the nineteenth century, Baron 

 Osten Sacken proved that the Bugonia fable had its 

 origin in the fact that the drone-fly lays its eggs upon 

 carcasses of animals, that its maggots develop within 

 the putrescent mass and resemble bee-larvae, and 

 finally change into a swarm of flies which, in their shape, 

 hairy covering and colour, look exactly like bees, 

 although they belong to a totally different order of 

 insects. " Thinking is difficult, and acting according 

 to reason is irksome," said Goethe. For more than 

 two thousand years people overlooked the likeness 

 between the drone-fly and the honey-bee, and believed 

 in a tradition which a single experiment would have 

 shown to be without the slightest foundation. 



We may forgive most people for holding such beliefs, 

 because they may have had no easy opportunity of 

 testing them by personal observation ; but it is remark- 

 able that writers on natural history should be content 

 to hand down statements of traditional authorities 

 without troubling to look for evidence of the beliefs 

 they accepted, or to examine for themselves the com- 

 monest natural facts. Perhaps the most extraordinary 

 case of this mental blindness is that of the colours of 

 the rainbow. In De Proprietatibus Rerum, written by 

 Bartholomew of England before the middle of the 

 thirteenth century, and translated into English in 1397, 

 the succession of colours in the rainbow is given as red, 

 blue and green. " This succession," says Prof. Miall, 

 " had a mystical meaning ; red was a symbol of fire, 

 blue of water, green of earth. For more than five 

 hundred years men went on repeating an error which 



