1 88 ENTOMOLOGY 



From this explanation, the superior value of Miillerian as compared 

 with Batesian mimicry is evident. 



The fourth condition that the imitators differ from the bulk of 

 their allies holds true to such a degree that even the two sexes of the 

 same species may differ extremely in coloration, owing to the fact that 

 the female has assumed the likeness of some other and protected species. 

 The female of Papilio cenea, indeed, occurs (as was just mentioned) 

 under three varieties, which mimic respectively three entirely dissimilar 

 species of Danais, and none of the females are anything like their male 

 in coloration. 



The generally accepted explanation for these remarkable but numer- 

 ous cases in which the female alone is mimetic, is that the female, bur- 

 dened with eggs and consequently sluggish in flight and much exposed 

 to attack, is benefited by imitating a species which is immune; while 

 the male has had no such incentive so to speak- 

 to become mimetic. Of course, there has been no 

 conscious evolution of mimicry. 



Wallace's fifth stipulation is important, but should 

 read this way: "The imitation, however minute, is but 

 FIG. 246 A external and visible usually, and never extends to in- 

 locustid, Myrme- ternal characters which do not affect the external ap- 



cop hana fallax, which ,, . ,11 



resembles an ant. pearance. For, as Poulton points out, the alertness 

 FronfB^uNNEiTvoN ^ a ^ eet ^ e which rnimics a wasp, implies appropriate 

 WATTENWYL. changes in the nervous and muscular systems. In 



'its intent, however, Wallace's rule holds good, and 

 by disregarding it some writers strain the theory of mimicry beyond 

 reasonable limits. Some have said, for example, that the resem- 

 blance between caddis flies and moths is mimicry; when the fact is 

 that this resemblance is not merely superficial but is deep-seated; the 

 entire organization of Trichoptera shows that they are closely related 

 to Lepidoptera. This likeness expresses, then, not mimicry, but affinity 

 and parallel development. The same objection applies to the assumed 

 cases of mimicry within the limits of a single family, as between two 

 genera of Heliconiidae or between the chrysomelid genera Lema and 

 Diabrotica. The more nearly two species are related to each other, the 

 more probable it becomes that their similarity is due not to mimicry but 

 to their common ancestry. 



On the other hand, the resemblance frequently occurs between species 

 of such different orders that it cannot be attributed to affinity. Illus- 

 trations of this are the mimicry of the honey bee by the drone fly, and 



