THE MEXICAN BEAN BEETLE 27 



Suitability of the Climate of New England for the Bean Beetle 



The practical value of the experin.ental data just presented can be esti- 

 mated by a study of the cliniatological data for New England from, the rec- 

 ords of the United States Weather Bureau. Temperature and precipitation 

 records from numerous places in this region have been secured for a number 

 of years, and a few stations have been collecting relative humidity changes. 

 The latter is more valuable in this study but, because of lack of sufficient 

 material, precipitation records also will be used. 



Faiin-al Zones of Nerv EnglancL 



The faunal zones occurring in New England are the Canadian of the Boreal 

 Region and Transition and Upper Austral of the Austral Region. These 

 zones, as shown in the United States Biological Survey map of 1910 with 

 modifications for New England by Fernald (1915 and later), are followed 

 (Fig. 6). Meteorological data collected by the United States Weather Bu- 

 reau stations within the various zones arei used to determine the temperature 

 and moisture conditions. Cliniatological data secured at places where the 

 zones overlap are not used. Stations in the various zones selected as suitable 

 for this study are shown in Figure (i. 



Upper Austral Zone. — A composite clin.ograph of temperature and mois- 

 ture for the Upper Austral Zone is shown in Figure 7. The mean relative 

 humidity is given in the climograph of Hartford, which is near the center of 

 the Upper Austral Zone (fig. 8, Mean). The lowest humidity ordinarily 

 occurs in the afternoon, and the 2 p. m. conditions plotted in Figure 8 (2 

 p.m.) approximate the driest part of the day. It is evident that the humid- 

 ity is plentiful throughout the year, thus assuring suitable conditions for de- 

 velopment of the eggs and larvae in summer and for hibernation of adults in 

 winter. If the temperature becomes excessive during the summer months, 

 the humid conditions would become unfavorable, but an examination of weath- 

 er records shows that extreme temperatures are imcommon and of short 

 duration. Maximum temperatures are ordinarily below 100° F. (37.8° C.) 

 and, unless continuing for several successive days, the temperature among 

 the plants fails to become injurious. Apparently conditions are favorable 

 for the bean beetle to becone a serious pest in the Austral Zone of Massa- 

 chusetts, Connecticut, and Rhode Island. Beans are a rather common garden 

 plant in this area. The insect is now found in this faunal division in south- 

 western Connecticut. 



Transition Zone. — The mean temperature and precipitation are shown in 

 the conposite climograph for this Zone in Massachusetts, Connecticut, Ver- 

 mont, New Hampshire, and Maine (fig. 9). A composite graph of the mean 

 relative himiidity and the 2 p.m. conditions of Boston, Portland, and Burl- 

 ington are given in Figure 10 (Mean, 2 p.m.). The precipitation and rela- 

 tive hiunidity in Maine, Massachusetts, and Connecticut are very similar to 

 that of the Upper Austral Zone just discussed. Since the temperature is 

 slightly lower, less danger to the insect from the comlbination of high tem- 

 perature and high moisture would exist. New Hampshire and Vermont are 

 somewhat drier, but the heavier precipitation falls during the growing sea- 

 son and would be satisfactory for development of the imimature stages. The 

 winter months are sufficientlv humid for successful hibernation of the adults. 



