276 MIMICRY AND NATURAL SELECTION 



animals ? Why should the mimics happen to belong to 

 a day-flying group, although moths are as a rule nocturnal? 

 All these questions receive an obvious answer when the 

 theory of Natural Selection is adopted as the explanation 

 of Mimicry : they cannot be answered by any other 

 existing theory. Under any other theory the facts are 

 gratuitous, devoid of meaning. 



When the model belongs to one insect Order and the 

 mimic to another, difficulties of interpretation, except on 

 the theory of Natural Selection, become even greater. 

 Why should the models in the vast majority of cases 

 happen to belong to the Hymenoptera and to possess 

 stings or other special modes of defence ? Why under 

 the totally different conditions of Borneo and South Africa 

 should a local Xylocopid bee be mimicked by a local 

 Asilid fly {Hyperechia) ? l Many moths come to resemble 

 transparent-winged Hymenoptera by losing, probably 

 during their first flight, scales which were present on their 

 wings when they emerged from the pupa. Is any one bold 

 enough to maintain that a resemblance thus caused is due 

 to External or Internal Causes or to Sexual Selection ? 



The assumption that local influences act uniformly on 

 different species is by no means justified except in the 

 case of species with similar habits and life-histories : Mr. 

 Guy A. K. Marshall has sent me a wonderful group of 

 reddish brown or ochreous insects with the posterior part 

 of the visible dorsal surface black. It contains many 

 species of the Lycid models, and also Coleoptera belonging 

 to the Telephoridae, Melyridae, Phytophaga, Cantharidae, 

 and Longicorns, several species of aculeate Hymenoptera, 

 a few Hemipterous insects, two species of moths and one 

 of Diptera. 2 We have here all kinds of habits and all 

 kinds of life-histories, larvae living in the open, larvae 

 burrowing in plant-stems, carnivorous larvae, leaf-eating 

 larvae, larvae with special food stored in cells. It is 



1 R. Shelford in Proc. Zool. Soc. Lond., 1902, pp. 261, 262 ; plate xxii, 

 figs. 1,2. G. A. K. Marshall in Trans. Ent. Soc. Lond., 1902, pp. 533, 

 534; plate xxii, figs. 19, 20. 



2 G. A. K. Marshall in Trans. Ent. Soc. Lond., 1902, pp. 515-18; 



plate xviii. 



