154 Journal of Agricultural Research voi. xiii.no.s 



OVERWINTERING OF ADULT FLIES UNDER NATURAL CONDITIONS 



Frequent obsen'ations were made during the winter on the occurrence 

 and behavior of house flies found living under natural conditions. For 

 convenience in comparison with the experimental results these notes are 

 summarized under the same headings. 



UNDER OUTDOOR CONDITIONS 



In the fall of 191 4 obsen'ations were begun early in November. Adult 

 house flies were found outdoors during warm days up to December 9. 

 On December i several house flies were collected at a compost heap on 

 the Arlington farm, and again on December 3. On this same date sev- 

 eral recently emerged flies were taken near a heap of pig manure at the 

 Bethesda farm. On December 9 many recently emerged flies were found 

 on a heap of horse manure at College Park, Md., but after this date none 

 were found outdoors until April, 191 5, when the following notes were 

 made: 



April 7. No Musca domestica taken. Qjllected Pollenia rudis Fabricius, Phorbia 

 cinerella Fallen, Sepsidae, and Borboridae. 



April 8. Swept from horse dropping in road Lucilia sericata Meigen, Orthellia corni- 

 cina Fabricius, Myospila meditabtinda Fabricius, Phorbia cinerella P'allen, Copromyza 

 equina Fallen, and an tnidetermined species of Scatophaga. 



April 10. Air temperature, 80° F., at 2 p. rn. Search was made at pigpens, stables, 

 manure heaps, etc. No Musca domestica found. Muscina stabulans Fallen was 

 collected . 



April 16. No Musca domestica found. Collected Pollenia rudis, Phormia regina 

 Meigen, Lucilia sericata, and others. 



Anril 25. A few house flies were taken by Max Kisliuk near stable at College Park, Md. 



April 30. One female house fly taken near stable at the Arlington farm. 



During the winter of 191 5-1 6 flies were found outdoors as late as 

 December 4. On that date one house fly was seen on wall on the south 

 side of one of the animal houses of the Bethesda Experiment Station. 

 No house flies were again found outside until the following April. Several 

 flytraps were set out at various places on the Bethesda station, some on 

 March 30 and others April 6, and were kept in operation throughout the 

 season. Many species were caught, including Pollenia rudis, Phormia 

 regina, Muscina stabulans Fallen, and M. assimilis Fallen, from the 

 beginning of the exposures, but Musca domestica put in its first appear- 

 ance on April 20, 191 6. * 



The records for the winter of 191 6-1 7 are similar. House flies were 

 collected as late as December 12, 1916, after which none were again taken 

 until the following spring. A few house flies put in an appearance at a 

 very early date this year. Two females and one male were taken in a 

 flytrap on March 26, 1917. A few scattered specimens were taken at 

 various times during April. The unusually early appearance of house 

 flies outdoors at this date was doubtless due to the fact that breeding 



