')4 Ohservafioufi cm the HahitR of Certain Flies 



been widely studied. The problem of fly-control may be dealt with by 

 three methods: (1) destruction of the adult; (2) destruction of the im- 

 mature stages; (3) perfect and thorough sanitation. 



Fhes are a corollary of insanitary conditions. "No dirt, no flies." 

 In those parts of modern cities, in \#hich strict sanitation is observed, 

 flies are. probably, not of great importance; but little hope can be enter- 

 tained of freeing the poorer parts of our own towns and cities, much 

 less those of Eastern countries, from the danger of their presence until 

 legislation and education are much improved. 



Method 3, therefore, entails, not only legislation but the alteration, 

 in many cases, of ancient habits, and so is not likely to be applied 

 immediately, still less universally. Method 1, as will be shown later, can 

 never be either thorough or permanent. 



Under these circumstances the importance of adopting the second 

 method cannot be too strongly advocated. There are, however, occasions 

 when circumstances necessitate the use of the first method ; for instance, 

 when either it is not possible to obtain authority to control the breeding 

 places; or they are too large to be dealt with by the means at hand. 



Since the house-fly {Musca domestica) has such a wide geographical 

 distribution, it is probable that its life history is variously modified in 

 different parts of the world. This modification will probably depend on 

 climatic conditions — especially those of sunshine and temperature — and 

 the presence or absence of insect and fungoid enemies. Portchinsky 

 (1913) writes that in July 1911 he found very large numbers of M. 

 domestica in and about the houses and stables of newly founded farms, 

 on the dry arid steppes, in the southern part of the (Jovernment of 

 Stavropol (N. Caucasus); that there were no Hydrotaea, Myospila medita- 

 hunda, or Polyetes albolineata, and that Muscina stabulans was rarely 

 found on these farms; and that in the open country away from the 

 houses M. domestica flourished in enormous numbers in the total absence 

 of their chief enemies. 



In England and countries with a similar climate, the year may be 

 divided into two seasons as regards -fly control — namely. May to the be- 

 ginning of November and from November to May (Graham-Smith (1916) 

 chart iy. In summer it seems hopeless to attempt to deal thoroughly 



^ This refers to flies generally. As regards Mu.sra domesticn the period during whii li 

 the adults are most numerous lasts from July to October. The remainder of the year 

 presents the weakest jiart of the life-history of the hf>use-fly. If breeding places were 

 rigorously attacked particularly at this season, the niimlxTs cuicrging l)ctwcen June and 

 October would be greatly diminished. 



