280 



ENTOMOLOGICAL NEWS. 



[June, '17 



fly season followed the period of highest average temperature 

 the last week of July and was initiated by an abrupt increase 

 in house flies the first week of August and ended with an 

 abrupt decrease during the fourth week. In September tem- 

 perature naturally decreases and is attended by a correspond- 

 ing decrease in the numbers of adult flies. It is a common idea 



TABLE SHOWING CATCH OF VARIOUS SPECIES OF FLIES BY WEEKLY PEKIODS, 

 AND AVERAGE PERIOD TEMPERATURES. 



in Montana that flies are most abundant in houses during Sep- 

 tember, though their number out-of-doors is materially less. 

 Observations have also indicated that other species besides 

 the house fly are more numerous in houses at this time. This 

 is probably because a greater proportion of flies are impelled 



* Determined by J. R. Parker. 



