3 I2 SCIENCE FROM AN EASY CHAIR 



flag," a warning to other animals that the yellow and black 

 animal had better not be bitten and tasted. So the 

 previous experience of animals who have bitten yellow 

 and black creatures is appealed to, and ensures the safety 

 of the yellow and black gentry from tentative bites which 

 would kill them. Other recognition marks by which ill- 

 tasting, nauseous butterflies are distinguished, and in con- 

 sequence of which they escape attack, and, not only that, 

 but are " mimicked " (as the yellow and black poisonous 

 wasp is mimicked by some innocuous flies which thus 

 escape attack) by other pleasant-tasting butterflies which 

 fly with them, are considered by Mr. Thayerto be wrongly 

 interpreted as recognition or " warning " marks. He 

 shows, with more or less success, that the markings of the 

 butterflies known as Heliconiae are effective as conceal- 

 ment, and is therefore inclined to deny their value as 

 "warning" marks, serving to indicate a noxious quarry 

 best left untasted. 



It is, of course, quite possible that what are " conceal- 

 ment markings" when viewed by an aggressive bird or 

 lizard at a distance, may be recognised as " warning 

 marks" when seen by the same observers at close 

 quarters, and it is also possible that the latter may have 

 become the more important or only important result of 

 the colour marks of a given butterfly which were once 

 useful as " concealment." The possible change of signifi- 

 cance of colour spots and markings in wild animals may be 

 illustrated by the effect on human beings of the burglar's 

 crepe mask. At the present moment probably the most 

 prominent result of the appearance in a house full of 

 people in the dead of night of a man with a crepe mask 

 over his face would be terror to those who saw him. The 

 mask would be interpreted as a " mark " or " sign " of evil, 

 not to say violent intentions on the part of the masked 

 man. It would be a "warning colour," and most un- 



