ZOOLOGY FOR MEDICAL STUDENTS CHAP. 



at 5 days in this stage? the adult fly emerges. About 7-10 days 

 the It-mule begins to lay eggs. 



during the adult phase that the fly becomes a source of danger. 



..lie in its tastes it is at one moment wandering about amongst and 



a human faeces, at another wading in the jam on a tea-table, 



nother creeping about food in course of preparation in a kitchen. 



Human faeces are liable to be crammed with microbes of diseases of the 



alimentary (anal, such as Diarrhoea, Typhoid, Cholera, Dysentery, and 



such microbes' taken into the alimentary canal of the fly are apt to remain 



alive and even in the case of bacteria to multiply within it. The fly 



when feeding, especially when feeding on sugar or other soluble material, 



ies from time to time a drop of clear fluid from its mouth and both 



this and the faeces of the fly are liable to infect the food on which they 



ieposiu-d. Portions of faecal material containing microbes are also 



liable to adhere to the feet or other parts of the fly and to be left behind 



\\hen it wades in jam or other food-material. Such disease germs lying 



in wait in food-material are obviously liable to infect with disease human 



who swallow them. 



It is clear that House-flies constitute a distinct menace to health, 



and therefore that their numbers should be kept down to the minimum 



about human habitations. The adult flies should be destroyed by 



AperSj "tangle-foot," 1 or poison. 2 But here again, as is the case 



with mosquitos, the most effective measures are those directed against 



the earlier stages of the life-history. The all-important thing is to 



prevent the accumulation of garbage, fresh manure, or faecal matter in 



s accessible to flies and in the neighbourhood of habitations. Such 



trials arc preferably incinerated: if they have to be accumulated, 



^cumulations should be buried under at least two feet of earth. 



The genus I-annia (or Homalomyid) includes the small House-fly (F. 



iniculuns) and the Latrine fly (F. scalaris), distinguishable from Musca 



by their smaller size, the greater overlap of the wings when at rest, the 



plain (not leathery) bristle of the antenna, and the fact that two nervures 



'her 62 parts of resin, 26 of castor oil, and 12 of honey. Dip 

 this and leave about. When well covered with flies 

 ii .1 llainu ami recoat the wire. 



" i lb. (or Cooper's Sheep-dip Powder 3^ Ibs.), sugar 10 



iter 10 gals. Owing to its very poisonous character 



ur this solution with some distinctive dye. Cloths moistened 



ung up ; or bottles of it may be left standing about with wick 



non. 



ly poison consists of 3 per cent Formaline in sweetened 

 ve about in rooms during the night in saucers, taking care 

 'i fluid is available for the flies to drink. 



