LEPIDOPTERA OF NEW YORK AND NEIGHBORING STATES 17 



combination of forms. It covers the area with a summer temperature 

 of 64 to 72, or a total growing heat (sum of daily excesses over 

 43) of 10,000 to 11,500F. 



The Upper Austral, or Carolinian, zone has a summer temperature 

 range of 72 to 79, or a total growing heat of 11,500 to 18,000 F. 

 It is the most northern area for many characteristic species: Papilio 

 marcellus (and its food, the papaw), cresphontes, philenor, Pieris pro- 

 todice, Eurema nicippe, Euptoieta claudia, Chlorippe clyton and celtis 

 (with Celtis, their food) and others, besides a large number of skippers. 



The most striking of the characteristic moths are Herse cingulata, 

 Phlegethontius sexta, and Citheronia regalis. Besides a part of the 

 Mississippi Valley, it embraces the extreme southern part of Ontario 

 and the Great Lakes strip of New York; but on the Atlantic Coast 

 it is more restricted, including the major part of Virginia and Mary- 

 land and sending long arms along the coast and up the rivers. Dis- 

 tinctively Austral forms even reach Albany on the Hudson, Spring- 

 field on the Connecticut, and Boston along the coast. Part of the 

 Austral species named are strong flyers, and also appear sporadi- 

 cally far out of their range, where they rarely or never breed. 



The lower Austral zone, or Austroriparian, scarcely enters the 

 region under discussion, but can be considered to include the coast 

 of Virginia, and possibly isolated points in Maryland, and Cape May, 

 New Jersey. Its summer temperature is over 79 F., and its total heat 

 is 18,000. Most probably in this case the total heat is the controlling 

 factor. 



Only a few lower Austral species are recorded in this monograph, 

 either those that are particularly striking or those that have been 

 often reported as strays in the North. In fact, our part of the area 

 has scarcely been studied. 



South. of this there is a series of tropical zones, which do not con- 

 cern us. 



The control of humidity is, in our region, less striking, as it limits 

 itself mainly to the setting off of the very damp off-shore islands, 

 where ground vegetation is rank and trees are often gnarled and 

 stunted. This strip has been so changed by man largely through 

 fires and sheep pasturing that it is no longer possible to say what 

 its natural stock was ; but it is particularly marked by a wide north- 

 ward range of species otherwise sub-tropical, like the Prenes and 

 Prionapteryx nebulifera, mixing side by side with the boreal forms. 

 This is perhaps because the blanket of fog masks the severity of the 

 winters; an effect that reaches an extreme on Nantucket, whose 

 indigenous Lepidoptera have now largely disappeared because of 

 sheep pasturing. 



