208 ENTOMOLOGY 



more commonly than has been generally supposed. At the same time 

 there is no proof that the viceroy profits at present by its mimetic 

 pattern, though it may have done so in the past. In any event, the 

 departure of ar chip pus from its congeners toward one of the Danainae a 

 famous group of "models" in the tropics is unintelligible except as an 

 instance of mimicry. 



Granting that mimicry is upon the whole advantageous, it becomes 

 important to learn just how far the advantage extends ; and we find that 

 mimicry is not of universal effectiveness. Even the highly protected 

 Heliconiinae and Danainae are food for some predaceous insects. In 

 this country, as Judd has observed, the drone-fly (Eristalis tenax) , which 

 mimics the honey bee, is eaten by the kingbird and the phcebe; the 

 kingbird, indeed, eats the honey bee itself, but is said to pick out the 

 drones; chickens also discriminate between drones and workers, eating 

 the former and avoiding the latter. Bumblebees and wasps, imitated 

 by many other insects, are themselves eaten by the kingbird, catbird 

 and several other birds, though it is not known whether the stingless 

 males of these are singled out or not. Such facts as these do not discredit 

 the general theory of mimicry but point out its limits. 



Evolution of Mimicry. Natural selection gives an adequate ex- 

 planation of the evolution of a mimetic pattern. Before accepting this 

 explanation, however, we must inquire: (i) What were the first stages 

 in the development of a mimetic pattern? (2) What evidence is there 

 that every step in this development was vitally useful, as the theory de- 

 mands that it should be? These pertinent questions have been 

 answered by Darwin, Wallace, Miiller, Dixey and several other 

 authorities. 



The incipient mimic must have possessed, to begin with, colors or 

 patterns that were capable of mimetic development; evidently the raw 

 material must have been present. Now Miiller and Dixey in particular 

 have called attention to the fact that many pierids have at least touches 

 of the reds, yellows and other colors that are so conspicuous in the heli- 

 coniids. More than this, however, Dixey has demonstrated as appears 

 clearly from his colored figures a complete and gradual transition from 

 a typical non-mimetic pierid, Pieris locusta, to the mimetic pierid 

 Mylothris pyrrha, the female of which imitates Heliconius numata. He 

 traces the transition chiefly through the males of several pierid species 

 for the males, though for the most part white (the typical pierid color), 

 "show on the under surface, though in varying degrees, an approach 

 towards the Heliconiine pattern that is so completely imitated by their 



