THE LEPIDOPTERA OR BUTTERFLIES AND MOTHS 23 



sucking proboscis ; marked changes take place in the 

 digestive organs which fit them for the very different 

 diet of the butterfly; and changes equally great occur in 

 many other parts of the body. 



One of our commonest and most striking butterflies 

 is the monarch, or milkweed butterfly. It has reddish- 

 brown wings with black veins and a dark border with 

 whitish spots. It is one of the few butterflies that are 

 migratory; it frequently travels southward on the approach 

 o.f winter, in large flocks. The larvae live upon milkweed 

 and may be recognized by their conspicuous black and 

 yellow stripes surrounding the body. The pupa is green 

 and hangs suspended by its cremaster. The pupa stage 

 lasts about two weeks, the species passing the winter as 

 an imago. 



Closely resembling the monarch in the color of its 

 wings is another butterfly of somewhat smaller size, 

 called the viceroy, Basilarchia archippus. It can be 

 most readily distinguished from the monarch by a black 

 bar across the hind wings. The viceroy is not at all 

 closely related to the monarch; the likeness is merely a 

 superficial resemblance in color. As the monarch butter- 

 fly is particularly distasteful to birds it is therefore 

 seldom troubled by them. The viceroy is commonly 

 supposed to derive more or less protection from its resem- 

 blance to the monarch, since the birds would readily 

 mistake it for the distasteful species. Such protective 

 resemblance of one species to another is called mimicry. 

 It is a curious fact that most of the other species of Basil- 

 archia are colored very differently from the viceroy. 

 There are a great many cases among butterflies in which 

 a species may resemble in a most striking manner distaste- 

 ful species of a quite unrelated group. At the same time 

 these " mimicking" species may depart in an equally 



