HABITS 8g 



the proboscis is mov^ed from one spot a depression in the sugar 

 is observed, and, if the fly has been previously fed on carmine, 

 red stains round its margin are often seen. In a number of 

 experiments carmine stains were noticed on sugar 60, 80 and 

 90 minutes and even five hours after feeding on carmine. 



" Infection experiments described later seem to prove that in 

 the case of flies recently fed on syrup the fluid is mainly liquid 

 regurgitated from the crop. When the crop is empty saliva 

 alone is probably made use of 



" A fly was very carefully watched sucking an apparently 

 quite dry layer of sputum. It put out large quantities of fluid 

 from its proboscis and seemed to suck the fluid in and out 

 alternately until a fairly large area was quite moist. Then as 

 much as possible was sucked up and the fl)' moved on to another 

 place." (Graham-Smith, 1910.) 



F. Experiments on defcEcation. 



" Flies which have access to abundant food defalcate frequently. 

 The faeces, consisting of thick brownish or yellowish semi-fluid 

 material, are deposited in single masses and quickly dry, forming 

 opaque raised rounded stains. Occasionally the stains are pear- 

 shaped. At ordinary temperatures flies fed on coloured syrup 

 do not deposit coloured faeces within two hours. The faecal 

 stains can be usually distinguished without difficulty from 

 * vomit ' stains. 



" Three diff"erent types of marks or ' spots ' have therefore to 

 be distinguished : (i) faecal deposits, round, opaque, often raised 

 and yellowish, brownish or whitish in colour; (2) 'vomit' 

 stains, round, with a small opaque centre and clear peripheral 

 portion, bounded by a darker zone, and (3) proboscis-marks left 

 on half dried material. 



" The extraordinary number of deposits, both fiscal and vomit, 

 left by well-fed flies, can be judged from a small number of 

 experiments which were made with the object of ascertaining 

 the number of deposits (faecal and vomit) produced. (Plate 

 XVIII, fig. 2.) 



"In the first series (A) 10 flies were given a single feed of 



