198 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



At all seasons this butterfly is extremely fond of flowers, and great 

 numbers sometimes may be seen where it is common about a flowering 

 bush, restlessly visiting the flowers, stopping at each for an instant. 



There is an extraordinary similarity of habit between the summer 

 form of our zebra swallowtail and PafiUo podalirius of southern 

 Europe and northern Africa, as I have seen it in the south of France, 

 and between the spring form and the brown and green Papilio 

 sarfedon of eastern Asia, as I have seen it in Japan. 



Seasons. — The zebra swallowtail first appears about the last week 

 in March, before the food plant has begun to put forth its leaves, 

 becomes common in the first week in April, and remains on the wing 

 until late in May, The females seem to appear simultaneously with 

 the males. A second brood appears in the first week in June, and 

 from that time on there is a continuous succession of fresh individu- 

 als until the autumn cold puts an end to their activities, usually 

 between the middle and end of October. 



There are 2, 3, or in some cases 4 broods a year, depending on the 

 ancestry of particular individuals at the end of the season. The 

 spring individuals are from overwintering chrysalids derived from 

 all the broods of the preceding summer, even including the first, 

 so that some of the spring individuals may be considered as represent- 

 ing a single annual brood. 



Forms. — Early-spring individuals (form marcellus ; pi. 49, figs. 

 1, 2) are small with the fore wings from 33 mm. to 37 mm. (usually 

 about 35 mm.) in length. The fore wings are short, the outer margin 

 being almost or quite at right angles with the lower margin. The 

 hair on the front of the head is abundant and long, forming a con- 

 spicuous tuft. The borders of the hind wings are deeply scalloped 

 and the tails are relatively short. The dark markings are restricted 

 and the pale bands are broad. On the fore wings the second dark 

 band, which runs from the costal margin to the lower border, in- 

 cludes a conspicuous light stripe which crosses the cell. On the hind 

 wings the inner light band almost reaches the red spot at the anal 

 angle, which last is large and is shaped like a broad S. There is no 

 light stripe along the abdominal fold. Only the extreme tip of the 

 tail is white. This form flies until about the last of May, but becomes 

 scarce after the middle of May. 



At the end of the first week in April slightly larger individuals 

 (form telwmmiides) appear and slowly increase in numbers. In 

 these the wings are somewhat longer, the black markings are slightly 

 more extensive, and the outer portion of the tails is conspicuously 

 bordered with white, which extends more than halfway to the base. 

 This form flies with the preceding, becoming relatively more abun- 

 dant, until about the last of May. 



Early in June tlie first individuals of the summer form (form 

 lecontei; pi. 48, figs. 1, 2) appear. These are large, with the fore 



