vii DEFENCES OF INSECTS 251 



extent of its distribution over the body of the 

 animal. If the colour is widespread, and cannot be 

 veiled during the period of rest, then it proclaims 

 itself to be in most part of warning significance. 

 When it is of importance for warning, no care is 

 taken to hide it, and the flight is slow, so that the 

 adornment is completely displayed. Where the 

 appearance has a sexual value alone the insect 

 mounts zealous guard over it for the especial purpose 

 of courtship. The flight then is swift and wary, 

 and a characteristic habit is to settle with sudden 

 abruptness. 



These two groups nevertheless pass into each other, 

 especially in the Tropics, where colours which strictly 

 are produced by courtship seem to be utilised 

 for warning purposes. In such cases the dis- 

 tribution of colour becomes more general, and the 

 habits indicative of nauseous species are assumed. 

 When warning appearance has been developed by 

 this method, the colours and patterns of the members 

 of each of the groups distinctly resemble each other, 

 with the same good results as when the similarity 

 in the warning colouration has arisen differently. 



The resemblance between certain species of un- 

 palatable insects is such that they may be said to 

 mimic each other. This fact was first observed by 

 Bates, and Fritz Mliller explains it to be to the advan- 

 tage of both species, seeing that the destruction of 

 life involved in the education of their enemies is shared, 

 and so falls less seriously on each independently- 

 These remarkable resemblances are comparatively 

 rare, but Professor Meldola applies the same explana- 



