48 POEM AND COLOUt;. 



the latter are different in fundamental structure. The edible mimic 

 escapes through its resemblance to a distasteful insect. This form of 

 mimicry is common. Edible butterflies mimic nasty ones ; moths mimic 

 butterflies ; flies mimic moths ; flies also mimic bees or wasps ; there are 

 abundant instances which can be cited among- Indian insects (figs. 6G-68). 



Another form of mimicry occurs when we find in one locality a large 

 number of insects with a general warning scheme of colour, say black 

 and yellow. Among all these insects having a similar colour scheme 

 some are genuinely nasty, protected by unpleasant taste, bad scents, 

 poisonous bite, sting, etc., so that birds will not willingly eat them. 

 Others are not unpleasant, but pretend to be so by " adopting " the same 

 scheme of colouring. This is called Mullerian mimicry and is also 

 common. It must not be thought that an insect can change its colour 

 voluntarily ; the colour of insects is fixed and all of a species are coloured 

 much alike ; but it is believed that in the evolution of insects, the species 

 " adopted ^^ or gradually acquired colour schemes, and so the warningly 

 coloured insects arose first and other species later. If we disbelieve 

 evolution, we may say that the mimics were made like the warningly 

 coloured insects, and any misconception due to the deficiencies of the 

 terms used will be avoided. A few insects are so coloured and formed as 

 to resemble unpleasant substances ; thus the larvae of the citrus butterflies 

 are not unlike the excrement of a bird and feed on the leaves in such an 

 attitude as to assist the resemblance (fig. 195) 



Fig. 68. 

 A common Fly {lejl) vliich Viimics Ihe common Bee (ru/li) mid so escapes 'its foes. 



{Magnijled.) 



Deceptive colouring is very common ; it is apparently designed to 

 deceive birds and is useful when an insect is in flight. The Leaf Butterfly 

 is an instance ; the upper wings are brightly coloured and the insect in 



