June, '16] PARKER: DISPERSION OF MUSCA DOMESTICA LINNAEUS 327 



rection may be directly determined by the action of the wind, or in- 

 directly, owing to the flies being attracted by any odors it may convey 

 from a source of food; (2) that the chief conditions favoring the dis- 

 persal of flies are fine weather and a warm temperature; the nature of 

 the locality is another considerable factor, as iyi towns flies do not travel 

 so far as in the open country, this probably being due to the food and 

 shelter (author's italics) afforded by the houses; (3) that under ex- 

 perimental conditions, the height at which flies are liberated and also 

 the time of day, influences the dispersal of the insects, when set free 

 in the afternoon they do not scatter so well as when liberated in the 

 morning; and (4) that, in the experiments made, the usual maximum 

 flight in localities where houses are numerous seems to be about a quarter 

 of a mile (author's italics), but in one case a single fly was recovered at 

 a distance of 770 yards; it should be noted, however, that part of this 

 distance was across fen land."* 



• Mr. J. Zetek (1914)^ liberated about 5,000 flies stained with an 

 aqueous solution of gentian violet to which a small amount of gum 

 tragacanth had been added at an extensive manure pile 2,500 feet 

 distant from Isthmian Canal Commission Hotel at Ancon, Panama. 

 Seventeen flies were recovered in several screened buildings in Ancon; 

 these were mainly Musca domestica Linnaeus and Hermetia illucens 

 (Linnaeus). The writer (1914),^ while conducting certain investiga- 

 tions for the Montana State Board of Entomology at Laurel, succeeded 

 in tracing flies by placing a thick syrup colored with a red fruit extract 

 at a privy; flies which fed on this were identified when recaptured by 

 the red contents of the intestinal tract which showed very prominently 

 through the ventral membrane of the abdomen. The experiment 

 was continued but three days. Twelve flies were recovered at resi- 

 dences up to a distance of 150 yards and two specimens, one Musca 

 domestica Linnaeus and one Fannia scalaris Fabricius, at a meat 

 market 300 yards distant. 



The experiments as outlined above have suggested to the several 

 investigators concerned somewhat different conclusions, both in re- 

 spect to the radius of dispersion and the factors which control it. The 

 work of Hine, Hewitt, Hindle and Parker have to do with dispersion, 

 wholly or in part, under city or town conditions. Other observations 

 noted concern flight across the open and under more or less rural 

 conditions. Hewitt and Hodge are of the opinion that flies travel 

 with the wind, while Hindle believes his work indicates that the di- 

 rection of flight is against or across the wind. In partial support of 

 the opinion of the two former writers, we have the observation of 



* Quoted from Review of Applied Entomologj', Vol. 2, Ser. B., Pt. 2, p. 39, Feb. 

 1914. 



