14 BIOLOGICAL SURVEY OF 



"Aii indication of the comparative mildness of the Mi. 

 Deserl climate in spile of its arctic Horn, is to be found in a 

 group of Japanese pines growing ;ii one of the gateways 

 north of the village of Bar Harbor, a tree so sensitive to cold 

 thai it is killed al tli»' latitude of New York, which yet has 

 lived on this island for twenty years without protection in 

 winter. 



In the remarks by Rand and Redfield on the plant distribu- 

 tion you will notice thai an exception is made of the maritime 

 flora, otherwise there is a "resemblance to the general flora 

 of the White Mountain region." This is, to a large degree, 

 equally true of the insects. The same trees and plants of 

 the two places have the same insect enemies, and these insects 

 in turn serve as hosts for the same parasites. The elevations 

 of the island are not sufficient for the arctic-alpine forms of 

 Mount Washington and the boreal species are more com- 

 monly found near the shores and in the vicinity of the lakes, 

 cold spring runs, and bogs, the more sheltered and southern 

 exposures probably harboring the greater number of austral 



species. 



Iii regard to the distribution of aquatic insects, as pointed 

 out by Dr. R. II. Howe, Jr., 4 cold bogs and ponds that are 

 spring \'vd have less extremes in temperature than ponds thai 

 are not thus supplied with water. Thus lie found boreal and 

 austral dragon flies living together in the same pond far be- 

 yond their normal limits of distribution. The pond in ques- 

 tion had a bottom temperature of 51°F. in summer and 36°F. 

 in winter — a range of only 15°. 



The distribution of most of the maritime insects is governed 

 comparatively little by the corresponding vegetation, although 

 the two frequently show a similar distribution. Tempera- 

 ture and a suitable environment are the principal factors. 

 A low muddy shore with considerable marsh and pools of 

 brackish water has an insect fauna of its own, and it is 

 these species that often show a very wide distribution. To 



'"The distribution of New England Odonata." Proc. Boston Soe. Nat. Hist.. 

 vol. ::<;. p. lid, 1921. 



