350 PHYSICAL GEOGRAPHY. 



7. Danaus Plexippus Latr. This butterfly ranges over the whole North 

 American continent from Atlantic to Pacific (excluding perhaps the Rocky 

 Mountain district), as far north as the annual isotherm of 40, and over 

 that portion of South America lying east of the Andes and north of Rio 

 de Janeiro, including, also, many and perhaps all of the West India 

 islands. It occurs throughout New England, but it is much more rare in 

 the northern than in the southern part, though even here it can hardly 

 be called abundant, for, usually, specimens must be captured singly. Yet, 

 now and again, it swarms, as in the autumn of 1871. In some localities 

 it is especially numerous, such places, for instance, as islands off the 

 coast, or broad sandy sea-beaches, where no Asclepias grows. Is it that 

 an innate propensity for geographical extension leads it to the last possi- 

 ble limit ? Mr. L. L. Thaxter states that it is found in great numbers on 

 Appledore, the largest of the Isles of Shoals, which has a surface of about 

 500 acres ; yet there is no trace of milk-weed upon any of these islands, 

 which he has thoroughly explored. It has not been recorded from the 

 White Mountains. 



8. Basilarchia Disippe Scudd. Within New England, Disippe occurs 

 abundantly in the south, sparingly in the north, although found in the 

 very heart of the White Mountains. Gosse does not record it from 

 Compton, Canada; and the northernmost points from which specimens 

 have been reported are Mt. Desert (Scudder), Waterville (Hamlin), and 

 Norway, Me. (Smith), the Glen, White Mountains, and Sudbury, Vt. 

 (Scudder). 



9. Basilarchia Astyanax Scudd. The general range of this butterfly 

 is similar to that of the preceding, though less extensive. It is tolerably 

 abundant in the southern parts of New England, and occurs about as far 

 north as the annual isotherm of 45, the northernmost points recorded 

 being Dublin (Faxon) and Milford, common (Whitney). 



10. Basilarchia Arthemis Scudd. This species of Basilarchia has a very 

 different range from the two preceding, its southern limits nearly co- 

 inciding with the northern boundaries of B. astyanax. In New England 

 it has not been taken south of Massachusetts, and but rarely in that state. 

 It is already common at Brattleborough, Vt., Walpole (Smith), Weare 

 (Emery), and Dublin, N. H. (Faxon and Leonard) ; but it is said to be 

 scarce in Milford (Whitney), and in the immediate neighborhood of 



