250 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 1 

 Map 3 



not known, but Grevilliiis' experiments certainly show that it is 

 produced by an outer air temperature of — 35°C. ( — 31°F.) and 

 our records from Durham would show that with nests of similar size 

 an air temperature of — 24°F. (— 31°C.) is fatal. 



