144 BUTTERFLIES AND MOTHS 



mimicked by Pierida and other butterflies, and by some day- 

 flying moths. 



A most remarkable example of mimicry exists in a South 

 African Swallow-tail Butterfly (Papilio cenea). The male insect 

 possesses the characteristic tails to its hind-wings, but these are 

 not present in the female, and she is utterly unlike her mate in 

 the colouring and form of her wings. Three varieties of this 

 female are known, each closely mimicking three different species 

 of the genus Danais which have been proved to be distasteful to 

 insect-eating birds. The Indian and African butterfly Hypo- 

 limnas misipus is another interesting example in which the male 

 is non-mimetic and quite unlike the female ; the latter mimicking 

 the nauseous Danais chrysippus. It would appear that the females 

 are far more often mimetic than the males, and Wallace accounts 

 for this by the fact that they are especially open to the dangers 

 of attack, owing to their slower flight when heavy with eggs and 

 when resting on the leaves of the plants upon which they deposit 

 their eggs. 



The mimicking insect almost invariably belongs to an edible 

 variety that but for its remarkable resemblance to the unpalatable 

 or dangerous species it copies would readily fall a prey to insect- 

 feeders. It is this form of protective resemblance which con- 

 stitutes true mimicry, and Wallace has defined the following general 

 condition as being characteristic of this class of protected insects : 

 " (i) That the imitative species occur in the same area and occupy 

 the very same stations as the imitated. (2) That the imitators 

 are always the more defenceless. (3) That the imitators are always 

 less numerous in individuals. (4) That the imitators differ from 

 the bulk of their allies. (5) That the imitation, however minute, 

 is external and visible only, never extending to internal characters 

 or to such as do not affect the external appearance." 



Several of our British Clearwing Hawk-Moths mimic different 

 species of Hymenoptera. Thus the Bee Hawk-Moths (Bombyli- 

 formis and Fuciformis) closely mimic the humble-bees, with whom 

 they may be seen in company on sunny days in early summer, 

 hovering over azalea and rhododendron flowers. The Hornet 

 Clearwing Hawk-Moths copy so closely in appearance the formid- 

 able hornet that it takes a very practised eye to detect the one 

 insect from the other while they are on the wing. 



