FAUNAL DISTRICTS OF NEW ENGLAND. 91 



thence abruptly to the northward. Skirting the eastern border of the 

 Champlain valley, it continues still northward to the valley of the St. 

 Lawrence as far as Quebec ; thence turning again south westward, it passes 

 along the northern border of the lowlands east of the Laurentian hills (in- 

 cluding the valley of the Ottawa), and crosses the southern peninsula of 

 Michigan near the forty-fifth parallel." (Bull. Mus. comp. zool.,ii: 

 395.) 



In 1883 Dr. A. S. Packard published two editions of a zoo-geographi- 

 cal map of North America, in which the great body of eastern North 

 America was separated into two divisions, a boreal or Canadian prov- 

 ince, and an Atlantic or eastern province. The dividing line between 

 these two, with the exception of a belt of the Atlantic province skirting 

 both sides of the Bay of Fundy, ran from the vicinity of the mouth of the 

 Penobscot north-eastward into the edge of New Brunswick, quickly 

 turned upon itself to follow a reversed course until it skirted the southern 

 borders of the White Mountains, when it again turned north-eastward 

 toward the Gulf of St. LaAvrence, striking it near the latitude of 70° W. ; 

 then it turned abruptly westward toward Lake Superior, following in all 

 this course, as stated by the author, the isotherm of 40° F. Outlying 

 islands of the Canadian province were indicated as found within the At- 

 lantic province in the Adirondacks region and on the summits of the Alle- 

 ghanies. 



Insects, it should be observed, are not regularly migratory animals ; 

 and since several generations frequently succeed each other during a single 

 season and winter is passed in very various conditions of existence, we can 

 hardly expect their distribution to follow exactly that of birds. Vari- 

 ous causes may modify unequally the distribution of insects belonging to 

 a certain group ; too intense cold in our arctic winters ; the lack of snow 

 during a less severe season ; too excessive heat or too long a drouth in 

 midsummer ; or, too sudden changes of temperature at critical periods. 

 To come to our butterflies, they may be found at all seasons of the year, 

 even in mid-winter, of one species or another, in every stage of existence, 

 from the egg, through all the larval stages and the chrysalis, to the imago. 

 The distribution of butterflies is therefore much more complicated than 

 that of bii'ds, whose early stages are always passed in comparatively warm 

 weather, under the guardianship of the mother ; and, if more than one 

 brood appears during a season, the second is only the produce of the same 

 pair that raised the first. 



It is nevertheless true that the distribution of insects over continental 

 areas coincides in a remarkable way with that of birds ; and the general 

 consensus of opinion, drawn not only from the study of birds but from 

 that of other animals as well, as shown by the views of the naturalists 

 already alluded to, and their agreement with the results of our own study 



