ooO [February 



the Mississippi, and perhaps about 36° on the Atlantic seaboard, the 9 

 Turn us is black ; that north of about 41° on the Atlantic seaboard, and 

 perhaps about 43° in the Valley of the 3Iississippi, the 9 Tunius is i/el'ow ; 

 and that in the intervening- district black and yellow females are intermin- 

 gled in varied proportions. Br, Fitch long ago remarked that southern 

 forms reach much higher latitudes in the Valley of the Mississi{)pi than 

 they do on the Atlantic coast and my own experience has led me to be- 

 lieve that the difference amounts to at least two decrees of latitude. 



Be this as it may, the fact is certain, that in some districts in the Uni- 

 ted States, the 9 Turnus is almost universally yellow, in others almost 

 universally black. If the question of normality is to be decided only by 

 the relative numbers of black and of yellow 9 9 , a Junj of Entomologists 

 would bring in one verdict at Cairo, and another at Boston; and at Phila- 

 delphia they would probably bring in no verdict at all. Numbers, there- 

 fore, cannot be a safe or a philosophical criterion on this point. 



We have a somewhat similar case, in the closely allied family Pieridae, 

 with the genus Co/ias. There are three species of this genus described by 

 my friend Mr. Scudder as occurring in boreal America, the S of which 

 is yellow and the 9 white.* On this account they are placed by that 

 writer in a section by themselves. But, as he himself adds, there are also 

 two kinds of 9 9 of the common C.pMlodice, one yellow, the other whit- 

 ish, but always either of one tint or the other with no intermediate grada- 

 tions, the white 9 being of great rarity. On account of this rarity of the 

 Vt^hite 9 ) i^Mlodice is placed by him in a section where the two sexes are 

 of the same color. At Rock Island C. pliilodice is very common and 0. 

 turytliemc Boisd. {C.ampMdu^a Boisd.) is also quite common, and in one 

 particular year white 9 9 belonging to one or the other of these two spe- 

 cies were very common, though generally they are rather scarce. Hence 

 if the question of rarity is to govern the question of normality, it would seem 

 to follow that at Rock Island in A. D. 1859 the normal 9 of a non-boreal 

 species of Collas was white, and in other years yellow, which is absurd. 



If intermediate grades occurred between the black and the yellow 9 

 Turnus in a State of Natvire, which so far as my experience goes is not the 

 case, (though, if Mr. Newman and Mr. Wood are correctly reported, they 

 bred intermediate specimens,) we might call this phenomenon a mere 

 variety. If, again, it occurred in both sexes, we might call it, as Mr. Scudder 

 has done, in the case of C. philodice albinism; and in the case of /-*. Tur- 



Proceedings Boston Soc. Nat. Hist, September 1862, p. 104 



