The Bionomics of SoiUk African Insects. 441 



several times attempted to seize the butterfly at tliis spot. 

 The observation seems to point to, at any rate, one use 

 of the eye-like markings which are common on the under- 

 sides of tlie wings of butterflies," viz. in order to attract the 

 attention of an enemy, and thus divert it from more vital 

 parts ("Colours of Animals," London, 1890, pp. 206, 207). 

 The same interpretation is suggested by the habits of 

 many species which expose an eye-spot as soon as they 

 settle, when they are likely to be seized by an enemy 

 which has marked them down to their resting-place, but 

 quickly lower the wings and conceal the spot, so that they 

 are far more likely to be concealed from an enemy which 

 has not been specially directed to the exact place by 

 seeing them alight. (Much confirmation will be found 

 on pp. 371-5, where Mr. Marshall's injured specimens are 

 described.) 



Such directive marks may well be an advantage in the 

 wet season, when enemies with an abundance of other 

 insect food are less keen in their pursuit of butterflies, 

 but in the far greater stress of the dry season we can 

 understand how they would become a danger, and how 

 the only chance of the survival of the species lies in the 

 adoption of a cryptic appearance, and cryptic instincts in 

 their most extreme and unqualified form. 



This explanation has much in common with that sug- 

 gested for the seasonal phases of Precis. Indeed, it is of 

 much interest to observe that nachtigaUi, the wet form 

 of P. ctrtaxia, has precisely the same relationship to the 

 dry form as that described above in Satyrin^. It is far 

 less cryptic than the leaf-Hke dry phase, but it is not 

 conspicuous. The ocelli on the under-sides of both Avings 

 and the strongly-marked hind margins, together with the 

 specially prominent apex of the fore-wing, are probably 

 directive characters which divert the attention of an 

 enemy from the vital structures, when the insect is at rest 

 with its wings closed. 



The relationship of the interpretation in Precis to that 

 j ust suggested in Satyrinm, and to that oftered in certain 

 smaller Acr?eas (see pp. 433-7), renders it on the whole 

 improbable that there is any alternation in degrees of un- 

 palatability corresponding to the alternation in the seasons. 

 There is, however, no a irriori difficulty in the hypothesis 

 that a higher degree of unpalatability may be correlated 

 with the conspicuous colouring of the wet phase of Precis; 



