548 THE ZOOLOGIST. 



supposition ; for, according to this theory, protective resemblance, as 

 we now see it, has been arrived at by the gradual accumulation and 

 improvement of colour variations which make for concealment, and 

 the protective value of such variations must essentially be, or have 

 been, of only a partial character. Admitting that the gambols of the 

 Whip Butterfly (presumably of a sexual character) lead the insect into 

 a certain amount of danger, yet, to ask us to believe that it thereby 

 " invalidates " the protection afforded it, when at rest, by its assimila- 

 tive colouring, against other enemies, and perhaps even against the 

 " Suruqua " itself, is, as Mr. Bateson puts it, referring to a different 

 assumption, " to ask us to abrogate reason." Further, the not unusual 

 fact, that animals exhibiting a very high grade of resemblance are yet 

 subject to a considerable amount of persecution, in no way invalidates, 

 but rather strengthens, this principle ; for it is evident that such a 

 degree of resemblance can only have been developed in response to a 

 similarly high degree of persecution, acting either now, or within 

 recent times. 



It will thus be seen that, on general considerations alone, the 

 above objections to the principle of protective resemblance must be at 

 once ruled out of court. It may be as well, however, to discuss the 

 case of Cicadas in more detail. In the first place, I cannot agree 

 with Mr. Distant that these insects are easily captured owing to their 

 shrill cries. All high-pitched, vibrating sounds of this kind are very 

 difficult to localise exactly, and with Cicadas I have noticed very 

 frequently, both with myself and others, that the distance of the insect 

 is invariably much underestimated. 14 But even when the tree on 

 which the Cicada is sitting has been ascertained, it must be very 

 cautiously approached, for many species are able to detect one's 

 presence at a distance of fifteen to twenty yards in open country, and, 

 on so doing, they will at once cease their call ; and although they will 

 generally permit a much closer approach than this, yet it is always 

 extremely difficult to locate the exact position of the sound on the 

 tree. Their habits, however, vary in this respect, and among the 

 dozen or more species which I have observed in various parts of South 

 Africa, I have found it to be a very general rule that their wariness is 

 inversely proportionate to their protective resemblance ; those species 

 which live on rough, knotted bark, or among dense foliage, permitting 

 one to approach much nearer than do those that rest on bare, smooth 

 trunks or small twigs. The above remarks apply to the calling of a 

 single insect ; but, when a number are calling together, it is still more 

 difficult to localise any particular cry; and, indeed, I have on several 

 occasions been driven out of a patch of machabel bush by the con- 



