PAPILIO III., IV., V. 
ond and third regular broods. And this shows how it may happen that Turnus 
shall be on the wing from early spring till frosts destroy the species in the fall. 
In the Catskills, the eggs are laid about the middle of June, and there is no sec¬ 
ond brood. Mr. Saunders speaks of the larvae, in Ontario, being full grown by 
14th July, and the eggs therefore must have been laid early in June; and Mr. 
Scudder tells us that throughout New England there is but a single brood. 
Turnus is remarkable for its peculiar dimorphism, which, so far as is yet 
known, is without a strict parallel among butterflies. We have in our fauna sev¬ 
eral established examples of seasonal dimorphism, as in Papilio Ajax, Grapta 
Comma, the three Phyciodes, Thar os, Phaon, and Vesta; several Pierids, Colias 
Eurytheme, and no doubt future observations will discover many more. In Ly- 
coena Pseudargiolas, the winter form is Violacea, and this last develops females 
of two colors, blue and black, in the south ; and but one, the blue, at the north. 
Violacea in this respect resembles Turnus , but the dimorphism of the latter is not 
seasonal, the same characteristics being found in every brood of the year. In 
Grapta Interrogationis, also, the dimorphism is not seasonal, and the two forms 
appear in every brood. But they are represented in both sexes, the males of each 
being as distinct from each other as are the females. There is also a dimorphism 
confined to the females of many species, as several of the Coliades, but it prevails 
wherever the species is found, and is not subject to geographical limitation. 
Now in Turnus, the males are always yellow, and to the north of a certain lati¬ 
tude, about 41° 30' on the Hudson River, and 42° 30' in Wisconsin, all the fe¬ 
males are yellow. Below these lines, as one goes southward, the black females 
appear, at first but rarely, then increase gradually in proportion to the yellow, 
until an equilibrium is somewhere reached, apparently between 39° and 38°. But 
I cannot learn that, after that, the black everywhere continue to increase at the 
expense of the yellow, though they seem to do so in certain districts, or large 
sections of country. In this part of West Virginia, lat. 38°, I have often taken 
yellow females in the garden and field, and while they seem to be never so com¬ 
mon as the black, yet they cannot in most seasons be called at all uncommon. 
But I am certain that in some years, or rather in particular broods of some 
years, the black form does greatly outnumber the other. This was so in mid¬ 
summer of 1876. For some cause the species was exceedingly scarce in the 
spring of that year, quite the reverse of what usually happens. During the 
month of July, however, when the new brood was flying, both males and females 
visited a field of clover within easy reach in swarms, and I made a special point 
of searching for yellow females, as did Mr. Mead, who was with me, and we were 
both struck by their exceeding rarity. In fact, but one only was taken during 
the time the clover was in bloom, though we must have seen hundreds of the 
