Vol. XXviii] ENTOMOLOGICAL NEWS. 2/9 



widely separated, the general conditions semi-rural and health 

 conditions very poor. Several previous investigations have 

 concerned the comparative abundance of flies indoors, but the 

 work herein discussed dealt with out-of-doors conditions. Its 

 principal object was to determine approximately the height 

 of the house fly season in Montana. Five places were selected 

 representing a variety of conditions and at each a single Hodge 

 trap was placed out-of-doors. Two traps were placed at resi- 

 dences, at one of which there was a privy, at the other a 

 stable; the third was placed in the rear of a meat and fish 

 market; the fourth, in the rear of a general provision store, 

 and the fifth near an old garbage hole in the rear of the labora- 

 tory. The traps were placed in exactly the same spot each 

 day. Collections were made on five days of each week (ex- 

 cept Saturday and Sunday) at eight o'clock in the morning. 

 New traps were immediately substituted and the pans rebaited 

 (with fresh beer). At the laboratory the flies were killed with 

 ether and the number of each species recorded for each place 

 of setting. A record was also kept of the noon temperature* 

 and daily weather conditions. The weather records were 

 found to be of no apparent significance. 



The results of the experiment are given in the accompany- 

 ing table, which shows that the house fly reached its greatest 

 abundance (height of fly season) during the first three weeks 

 in August and was present in abundance during the whole 

 month. t It is interesting to note that the height of the house 



♦During the first week temperature records were taken at three in 

 the afternoon which doubtless accounts for the fact that the average 

 period temperature was higher for the first week than for the second 

 as shown in the table. 



fThe decrease in the record for the second week in August was due 

 to the fact that during the collecting period of that week, a pile of lum- 

 ber was placed where the trap was usually set in the rear of the meat 

 market. The results were materially affected because this was the 

 point where most of the flies were captured. The record for this week 

 (2266) shows a decrease of 8265 Mitsca domcstica from the number 

 captured at this place during the first week in August and a decrease of 

 9680 from the number captured the third week. A record correspond- 

 ing to those of the first and third weeks would have brought the total 

 for the second week well above 20,000. 



