74 The Ottawa Naturalist. [Oct. 



MIMICRY— SOME OF NATURE'S STRATEGEMS. 



By B. C. Tillet, Hamilton, Ont. 



Nature teems with instances of what are called mimetic re- 

 semblances, instances of organisms closely imitating their neigh- 

 bours for the sake of some advantage to be gained thereby. Thus 

 is instituted a sort of system of false pretences, an elaborate series 

 of confidence tricks which in their most interesting examples 

 have the merit at least of being defensive rather than aggressive. 

 It is rather curious that while protective colouration in the general 

 sense has certainly been elaborated, not only for defence but for 

 attack also, that manifestation of it, technically termed mimicry, 

 seems to have been developed solely for the purposes of defence 

 and escape. 



The gradation between ordinary protective colouration and 

 the most highly specialised form of mimicry is practically com- 

 plete. Our green caterpillars, our butterflies with brown under- 

 sides to their wings, the colouring of certain birds, and the mark- 

 ings of certain birds' eggs, are all instances of ordinary coloured 

 organisms. They do not resemble anything in particular. Their 

 colours are such that in most of their daily circumstances they 

 harmonise in a general sense with their surroundings, thus ceas- 

 ing to be specially noticeable, at any rate so long as they are at 

 rest. A further step is illustrated by the caterpillars of those 

 geometers usually called stick-caterpillars. These caterpillars are 

 of such form and colouring that when stretched out stiffly, they 

 have a strong resemblance to short dead twigs, sometimes even 

 with buds and leaf-scars complete; while, to render the illusion 

 quite perfect, they have also acquired the habit of resting in just 

 the very poses that twigs inight themselves take up. No better 

 example of this can be found than the caterpillar of Ennomos 

 magnarius, which when poised by the hind feet on a twig, with 

 the body thrown backwards into space, may well escape detec- 

 tion by all except the keenest observer. Perhaps one of the inost 

 remarkable examples of special protective resemblance is seen 

 in the leaf butterfly of Malay, Kallima paralecta. The wings of 

 this insect so exactly resemble a leaf when closed, that it may 

 pass altogether unnoticed. We find an elaboration here again 

 of the protective instinct. These insects have a rapid flight, but 

 they will drop suddenly and closing their wings as they alight, 

 take on all the appearance of a leaf. Thus, they seem to com- 

 pletely vanish. The protective instinct may be observed in many 

 insects. A butterfly which has been captured, fearing destruc- 



