LEPIDOPTERA 



743 



form are faintly indicated, especially on the lower surface, by a darker 

 shade. The marginal row of yellow spots is present, and also the 

 orange spots and blue scales of the hind wings. This form is repre- 

 sented only by the female sex, and occurs only in the more southern 

 part of the range of the species, i.e., from Delaware to Montana and 

 southward. It was the first of the two forms to be described, hence 

 the species bears the name glauciis. 



The zebra swallow-tail, Iphiclides marcellus. — This butterfly (Fig. 

 950) differs from all other swallow-tails found in the eastern half of 

 the United States in having the wings crossed by several bands of 

 greenish white. This is one 

 of the most interesting of 

 our butterflies, as it occurs 

 under three distinct forms, 

 two of which were con- 

 sidered for a long time dis- 

 tinct species. Without tak- 

 ing into account the more 

 minute differences these 

 forms can be separated as 

 follows. 



(i) The early-spring 

 form, Iphiclides marcellus 

 marcellus .—This is the form 

 figured here. It expands 

 from 65 to 70 mm. ; and the 

 tails of the hind wings are 

 about 15 mm. in length and 

 tipped with white. 



(2) The late-spring form, Iphiclides marcellus telamonides. — This 

 form is a little larger than the early spring form and has tails nearly 

 one-third longer; these tails are bordered with white on each side of 

 the distal half or two-thirds of their length. 



(3) The siunmer form, Iphiclides marcellus lecontei. — -The sum- 

 mer form is still larger expanding from 80 to 87 mm., and has tails 

 nearly two thirds longer than the early spring form. 



The life history of this species has been carefully worked out by 

 Mr. W. H. Edwards. He has shown that there are several generations 

 each year, and that the winter is passed in the chrysalis state. But 

 the early-spring form and the late-spring form are not successive 

 broods; these are both composed of individuals that have wintered 

 as chrysalids, those that emerge early developing into marcellus 

 marcelhis, and those that emerge later developing into marcellus 

 telamonides. All of the butterflies produced from eggs of the same 

 season, and there are several successive broods, are of the summer 

 form, marcellus lecontei. 



The larva feeds upon papaw {Asimina). This insect is found 

 throughout the eastern half of the United States except in the ex- 

 treme north. 



950. — Iphiclides marcellus. 



