The house-fly, Musca domestica Linn: its structure, habits, development, relation to disease and control . ptionof the drop. The drops are slowly extruded and then fly which I had under observation alternately and regularlyregurgitated and absorbed a drop of fluid eight times, each regurgi-tation and absorption lasting one and a half minutes. In somecases these vomit drops are deposited upon the surface on whichthe fly is resting and they may be easily recognised as light-coloured opaque spots (see fig. 35). Their colour will, of course,vary according to the nature of the flies l
The house-fly, Musca domestica Linn: its structure, habits, development, relation to disease and control . ptionof the drop. The drops are slowly extruded and then fly which I had under observation alternately and regularlyregurgitated and absorbed a drop of fluid eight times, each regurgi-tation and absorption lasting one and a half minutes. In somecases these vomit drops are deposited upon the surface on whichthe fly is resting and they may be easily recognised as light-coloured opaque spots (see fig. 35). Their colour will, of course,vary according to the nature of the flies last meal. Graham-Smith found that flies fed on coloured syrup often regurgitatedcoloured fluid 24 or more hours later, though fed in the intervalon uncoloured syiup. In his infection experiments he observedthat when infected food has been given, the infecting organisms. IMPORTANCE OF REGURGITATING HABIT 81 aro nsnally tound in great nunibers in these spots and niorec^ver,as will be shown later, fluid regurgitated from the crop is used todissolve or moisten sugar and (jther similar dry food materials.*. Fig. 35. Portion of window pane from fiy-infested cow-shed, showing dark-coloured faecal spots and more numerous light-coloured vomit spots. Naturalsize. The importance of this habit, from the point of view of bacterialcontamination, cannot be emphasized too strongly. The rate of digestion depends chiefly on the temperature andthe nature of the food. At (ordinary room temperatures the H. 6 82 THE HABITS AND BIONOMICS OF THE HOUSE-FLY coloured faeces produced by feeding flies on coloured syrup are notdeposited until several hours after the meal. Graham-Smith inhis experiments found they were not depijsited within two hoursafter feeding. He made a number of interesting observations onthe rate of defaecation and the effect of different kinds of food onthe same. The yellowish to dark broAvn faecal spots or fly specksare Avell known. A series of ten flies which had been given on
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