358 



ELEMENTARY BIOLOGY 



The explanation that is sometimes given of this resemblance is as 

 follows: The milkweed butterfly has a bitter or disagreeable taste, 

 and therefore birds commonly avoid eating the insect. The viceroy 

 belongs to a family that is commonly eaten by the birds, being suffi- 

 ciently attractive to them. The resemblance between the viceroy and 



the monarch protects 

 the former from the at- 

 tacks of the birds. Of 

 course it is not sup- 

 posed by anyone that 

 the viceroy butterflies 

 have purposely mim- 

 icked the monarch. It 

 is only supposed that 

 the resemblance, how- 

 ever it may have come 

 about, is of advantage 

 to the insects. We do 

 not understand how 

 these resemblances, or 

 others like them (see 



3 4 



FIG. 175. Supposed cases of mimicry 



/, Bombus pennsylvanicus, a bumblebee, mimicked by 2, 

 Laphria thoracica ; j, Vespa maculata, a wasp, mimicked 

 by 4, Spilomyia fuscia. In these cases the models and 

 the mimics belong to entirely different orders of insects, 

 the former are hymenoptera, or bee order ; the latter 



are diptera, or fly order FigS. 174, 175), have 



come about. Some of 

 the theories offered to explain them are discussed in Chapter LXXXIV. 



We are in doubt not only as to how such protective mimicry may 

 have arisen ; we are also in doubt as to whether mimicry is in all 

 cases protective. 



Professor Punnett, an English biologist, made a special study of 

 this subject in Ceylon, where examples of mimicry are unusually 

 abundant. He found, in regard to certain cases, that the model and 

 its supposed mimic never occupied precisely the same area ; at most, 

 the two areas overlap more or less. In the second place, the com- 

 mon birds, against which the mimicry is supposed to be protective, 

 do not molest either the model or the mimic ; but the lizards eat 

 the mimic as well as the other members of the family, which are 

 supposed to be defenseless. The only other serious enemy of these 

 butterflies was a certain large fly that pierces the thorax of the 

 insect and sucks the juices. But this fly, like the lizard, attacks the 

 mimic and his defenseless cousins without discrimination. In other 



