46 



FORM AND COtOUR. 



the imago, wliicli usually eoinmencos to apj)eav in the last moult but 

 one or two. There are countless instances of these changes and we may 

 constantly see instances of cryptic colouring-. 



On the other hand, we find some insects very vividly and brightly 

 coloured, so that they stand out strongly against their surroundings. 



Fia. G3. 



The South American Caterpillar ivhich suggested " warning colouration ''; tJie light bunds 

 are bright gellow, the feet and process red. 



These insects are usually distasteful to birds and predaceous insects 

 either from their taste, odour, or the oils they excrete. Their striking 

 colouration is accordingly supposed to be " warning ", i.e., warns the 

 birds that the insect is unpleasant. A young bird eating such an insect 

 associates the bright colours with the unpleasant taste ; it then refuses 

 to eat similarly coloured insects and warningly coloured insects escape. 

 There are many insects supposed to be warningly coloured ; red, orange 

 or yellow with black are common warning colours. Most bees and wasps, 

 ladybird beetles, some blister beetles, and some butterflies are so coloured. 



Fio. 64. 

 Moth of the precious Caterpillar, coloured cryptically in grey and hlacl. 



