7(58 ZOOLOGY INSECTS. 



America passed at once to a warm-temperate on account of the extension 

 of the continent into the arctic zone, while the climate of Europe passed in 

 succession through a tropical and then subtropical condition before becom- 

 ing adapted to the well-being of organisms requiring a moderate tempera- 

 ture (see Dana, Geology, p. 532). Hence we may regard these varieties of 

 C. album as nascent species ; our corresponding forms, having been long sub- 

 jected to the action of natural selection and other segregating causes, have 

 established themselves as independent species. 



GEAPTA HYLAS, Edw. 

 Grapta Hylas, EDW., Traus. Am. Ent. Soc., 1872. 



This pretty species seems quite local ; in this respect resembling its near 

 congener, G. Faunus. The first specimens were seen quite high up the 

 mountain, near Berthoud's Pass, August 16, where, at a small patch of flow- 

 ering plants, fifteen specimens were netted in the course of half an hour. 

 A few G. Zepliyrus were seen in the same locality. On the 28th, about 

 twenty miles from the South Park, on the South Park road, a few more 

 were found, with many Zepliyrus and some Vanessas. 



G. Hylas is uniformly smaller than Faunus, and the exquisite gray mar- 

 bling of the under surface is quite different from the marking of any Grapta 

 with which I am acquainted. 



Mr. Scudder has ranked this species as a dimorphic form of G. Zepliyrus, 

 but for this he gives no reason, and I am at a loss to imagine one, unless it 

 be assumed that every Grapta is necessarily dimorphic, and that only Hylas 

 can correspond to Zepliyrus. 



It seems to me, though possible, highly improbable that this will prove 

 to be the case, as Zepliyrus is much like Progne, and the characteristic mark 

 of the under surface of secondaries is angular as in that species, while that 

 of Hylas is a well formed C, resembling the mark of Faunus or Comma. 



It seems also unnecessary to create a possible synonym for Zepliyrus 

 true type (= var. Thiodamas, Scudder) before any experiments in rearing 

 the two species have been made. The case of Faunus and Gracilis is similar 

 to this, and here the only experiment in rearing which has been tried gave 

 a negative result ; the female Gracilis, which Mr. Scudder obtained, refused 

 to lay eggs upon the food plant of Faunus (willow), and thus died. 



