1916 ENTOMOLOGICAL SOCIETY. 99 



animals feeding on those plants, unless satisfactory substitutes can be found. The 

 cold of winter holds many forms in close agreement for their northern limit with 

 certain isothermal lines, and by a study of these and other factors, a general under- 

 standing of the zonal areas can be obtained. 



At the present time investigations on this subject are mainly by preparing 

 faunal and floral lists for different localities, particularly from places presumed to 

 be near the borders of the zones, and as a whole the latest results seem to indicate 

 that the Upper Austral Zone extends farther north than was formerly supposed to be 

 the case. It is, of course, recognized that no absolute line separates the zones, but 

 that they overlap somewhat along their edges, leaving more or less of a " debatable 

 ground,'^ but despite this, approximate limits have a significance when it comes to 

 the selection of the most successful crops to raise in any locality, and even local 

 modifications are worthy of consideration. 



The speaker regrets a lack of knowledge of local conditions of Canada as bear- 

 ing on this point. Certain examples from cases with which he is familiar, how- 

 ever, may be suggestive and be possible of application here. 



The State of Massachusetts is mountainous at its western end, numerous 

 peaks reaching a height of more than 2,500 feet, and that whole portion of the 

 state is more than a thousand feet high. East of this the state is crossed by the 

 broad 'Connecticut Eiver Valley, where, except for a few hills, the elevation is every- 

 where less than 500 feet. The central part of the state is higher again, the general 

 elevation of the land except for narrow grooves cut by streams, being over a thousand 

 feet. The eastern thii'd of the state, however, is all less than 500 feet above sea 

 level. 



So far as elevation goes, therefore, the eastern part of the state and the Con- 

 necticut Valley should haVe much in common. Such differences in elevation in 

 the state as have been indicated should not be of such importance as to aflEect 

 apple raising, for instance, but they do result in the appearance of minor differ- 

 ences which all have their effect. 



But even two such similar areas as the eastern end of the state and the Con- 

 necticut Valley have their differences. Nearness to the ocean has its effect in the 

 former case, moderating the temperature somewhat in winter, and slightly checking 

 excessive heat over extended periods in summer. But when southeastern Massa- 

 chusetts is considered, yet another difference is found. Here the influence of the 

 Gulf Stream as it sweeps northward modifies the winter and lengthens the fall, 

 preventing frosts until much later than only a few miles farther inland. 



The Gulf Stream is itself a somewhat variable factor. From time to time its 

 course changes, sometimes swinging in quite close to the land, while at others it 

 turns more out to sea, thus having less effect. In general, however, the result is that 

 crops normally grown only much farther south can be successfully raised on Cape 

 Cod and along the shore towns of the southern part of the state, besides insuring 

 safety to late planted crops coming onto the market after the regular season has 

 ended. 



Small factors sometimes prove to be of considerable importance in establishing 

 the limits of life zones, and this is illustrated by the Holyoke range of mountains 

 in the Connecticut Valley. This range is by no means a continuous one, but its 

 general trend is across the valley with an average height of perhaps a thousand 

 feet. In spite of its numerous breaks which would seem to render it of no import- 

 ance as a line of separation, we find many forms of life extending from the south 

 as far as this range but no farther, and the season on the northern side of the 

 range is about ten days later in spring than on tlie southern side. Tlie steep 



