February, '15] 



BROWN-TAIL MOTH DISCUSSION 



87 



year and have carried on very successful cooperative work with Pro- 

 fessor O'Kane in New Hampshire. 



Mr. W. E. Britton: Knomng as we do the general tendency of 

 the brown-tail moth to spread toward the north and east, I think it 

 would be interesting if Dr. Hewitt would explain why the southern 

 end of Nova Scotia is not generally infested. 



Mr. C. Gordon Hewitt: Answering these inquiries as they are 

 made, I would like to say in reference to Mr. Burgess' remarks concern- 

 ing the effect of humidity, that we find in Nova Scotia, judging from 

 our own results along here (indicating on the map), that the average 

 minimum temperature is higher than the minimum temperature in the 

 interior of New Brunswick. Owing to the occurrence of greater hu- 

 midity along the shore of the Bay of Fundy than in New Brunswick, 

 we find a greater percentage killed at a higher minimum temperature. 

 It is very evident that humidity exercises a very great influence along 

 this region in Nova Scotia (indicating the Annapolis Valley), where 

 the fogs are effective. 



In regard to Dr. Britton's inquiry as to w^hy the central region of 

 the eastern part of Nova Scotia is not infested, I cannot explain that 

 except in the absence of the chief food plants. This portion of Nova 

 Scotia (indicating) has a very peculiar geological formation. It is 

 largely coniferous and unsettled except here and there. Such occu- 

 pied lands are usually infested, but we never found any webs in the 

 scouting trips which have been made across the forest and lake region. 

 The large flight in 1913 resulted in the infestation of the southeastern 

 region including Shelburne County. We had observations made on 

 Sable Island by the lighthouse people, who collected and submitted 

 for examination all the moths they could capture at the light. We 

 did not find a single brown-tail moth but we found moths of the army 

 worm in these collections. 



A Member: What is the minimum temperature in New Bruns- 

 wick? 



Mr. C. Gordon Hewitt: The minimum temperature in New 

 Brunswick in the infested region last year, I think, was, so far as our 

 records show, 30.5 degrees below zero at St. Stephens. We found in 

 Nova Scotia that one hundred per cent of the larvae were killed at a 

 number of points where the temperature went to 22 degrees below. 



A Member: In New Hampshire as high as 95 per cent have been 

 found alive at a temperature of 30 degrees below. 



Mr. C. Gordon Hewitt: We found them in New Brunswick with 

 minus 30.5 degrees Fahrenheit temperature. 



President H. T. Fernald: We will now pass to the next paper 

 by Mr. C. H. Hadley, Jr. 



