HISTORY OF ZOOLOGY. 



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clumsy and yet unmolested by birds, because they contain bad- 

 tasting fat bodies. Another species of butterfly accompanies them 

 (Pieridae), which does not taste bad. and yet are not eaten, because 

 in flight, in cut, and marking of the wings they imitate the' 

 HeliconidB so closely that even a systematist might easily be 

 confused (fig. 13). In a similar way bees and wasps, feared on 

 account of their sting, are imitated by other insects. In Borneo 

 there is a large black wasp, whose wings have a broad white spot 



FIG. 14. a, Mygnimia aviculus, a wasp imitated by a beetle: b, Coloborhombus fascia- 

 tipennis. (After Wallace.) | nat. size. 



near the tip (Mygnimia aviculus). Its imitator is a heterornerous 

 beetle (Coloborhombus fasciatipennis), which, contrary to the habit 

 of beetles, keeps its hinder wings extended, showing the white spot 

 at their tips, while the wing-covers have become small oval scales 

 (fig. 14). 



Sexual Selection is a special phase of natural selection, chiefly 

 observed in birds and hoofed animals. For the fulfilment of his 

 sexual instincts the male seeks to drive his competitors from the 

 field, either in battle or by impressing the female by his special 



