256 CONTROL OF FLIES 



the flies from emerging, if, owing to the neglect of suitable 

 precautions, eggs have been deposited before the night soil is 

 covered. If considered desirable, some material may be added 

 to kill any larv« which may be present. Much attention has 

 already been paid to this subject, and the various methods which 

 have been adopted or suggested need not be given in detail. 



CHAPTER XXVIII 



SUMMARY AND CONCLUSIONS 



The subjects chiefly considered in each chapter, and the 

 conclusions arrived at, are here briefly recapitulated. 



The common-house-fly, Musca doviestica, occurs in all parts 

 of the world, and is the fly most commonly found in houses. In 

 the height of the fly-season at least 90^0 of the flies caught on 

 sticky papers or in traps belong to this species. In the earlier 

 months F. canicularis often predominates, but is displaced later 

 by M. doviestica. Many other species of non-biting flies, nearly 

 all of which frequent putrefying substances and fajcal matter, are 

 found in houses in small numbers. Owing to the numerous 

 hairs scattered over their bodies and legs, most of these species 

 are well adapted to carry bacteria from the substances they 

 visit, and to distribute them on food materials within a few hours 

 of contamination (Chapter ll). 



M. doniestica breeds mainly in heaps of fermenting materials, 

 especially piles of horse manure, but also breeds in refuse of all 

 kinds and in human faeces. The females frequent these sub- 

 stances for the purpose of laying eggs, and at the same time 

 walk over them and feed on them. The life-cycle from &^^ to 

 sexual maturity is completed under favourable conditions in 

 three to four weeks. The larvae of the house-fly together with 

 those of closely allied species, and members of the genus 

 Pycnosoina, are found in trenches in which night soil is buried 

 near camps and stations in the tropics (Chapter III). 



