12 Habit and Instinct. 



into his borrowed shell, but to seek and insert himself into 

 one suitable to his size; nay, farther, in the case of 

 Pagurus, he may even affix to his shell a sea-anemone 

 (Adamsia), the distastefulness of which to fishes will pre- 

 vent his falling a prey to their voracity. 



In many familiar cases of mimicry, specific activities 

 are correlated with mimetic structure and appearance. A 

 not uncommon beetle (Clytus arietis), which is mimetic of 

 the wasp, has a fussy manner, unlike the usually staid 

 demeanour of beetles, which serves to make the mimicry 

 more effectual. There occurs at the Cape of Good Hope 

 a harmless, egg-eating snake (Dasypeltis scabra), which 

 flattens its head, coils as if for a spring, hisses, and darts 

 forward as though about to strike, in a way that closely 

 resembles the characteristic mode of the berg-adder (Vipera, 

 atropos), of which it is mimetic. It is really quite harm- 

 less, subsisting on eggs, the shells of which are broken 

 in the throat by the enamel-tipped processes of the verte- 

 brae, which project into the gullet and form the so-called 

 gular teeth ; but its resemblance both in form and be- 

 haviour to a venomous snake presumably affords it pro- 

 tection from enemies. Mimetic resemblance may also be 

 of service in stealing upon prey. Thus hunting spiders, 

 which resemble the flies on which they feed, rub their 

 heads in very much the same way as do the flies them- 

 selves. These mimetic activities, which are probably truly 

 instinctive in their nature, must not be regarded as con- 

 sciously imitative ; they are, rather, analogous to the 

 mimetic appearance, and, like it, due to natural selection. 

 A great number of other instinctive activities might be 

 adduced in illustration of the fact that they are performed 

 in subservience to the general welfare of the organism, 

 and under circumstances which are of frequent recurrence 

 in the life of the individual and of the species. 





