Cryptic resemblance of huo South American Insects. 537 



these patches are traversed by a network of black pigment 

 enclosing in its meshes scales of a lighter but still dark 

 tint. This, although not well seen in Fig. lA, is especi- 

 ally clear and well defined in the chief patch alluded to 

 above. 



It is evident that the network covering the dark patches 

 represents at another stage the network with transparent 

 and pale meshes. It is probable that the former corre- 

 sponds to the fullest activity in the life of a leaf-destroying 

 fungus, the latter to its ultimate effect. It has been 

 already suggested that intermediate stages are represented 

 on the under surface of the hind-wing. 



Comparing these two surfaces of the wings we see that 

 the under possesses a pattern of varied and complex 

 detail, representing as I believe prominent stages in the 

 destruction of a dead leaf by a fungus. The upper surface 

 on the contrary exhibits a pattern strong in contrast but 

 deficient in detail ; representing only the ultimate effect 

 of such an attack upon the tissues of a dead leaf The 

 pale meshes are not only paler than on the under surface, 

 but the margins of the networks appear to be cleanly and 

 sharply punched through the substance of the wing. 

 The difference in this respect between the upper and 

 under surface is fairly well brought out by the figures, 

 especially when the right side of Fig. 1 is compared with 

 the left side of Fig. 1a. 



It seems to me possible that this wide difference 

 between the surfaces is an adaptation associated with the 

 normal position assumed by the moth : that in the 

 usual attitude of prolonged rest the under surface is well 

 illuminated while the upper is in comparatively deep 

 shadow. If approached from the well-lighted side all the 

 detail would be apparent ; if from the dark side the light 

 would be seen shining through the meshes. The upper 

 surface has developed, on this hypothesis, all that could 

 be seen on the shaded side of a dead leaf undergoing 

 destruction by the attack of a fungus, the under surface 

 all that could be seen on the well-lighted side. 



There is however another more probable interpretation 

 which suggests itself, — that the fungus model is a species 

 which attacks the leaf on one surface only, presumably the 

 lower, finally destroying the tissues as far as the upper, 

 cuticle or even so far as to cause complete perforation. And 

 the final stage, that of transparency, would then be seen on 



