84 HABITS 



on warm days, is no doubt due to its anxiety to feed on the 

 skin secretions. 



Flies deposit vomit and faeces on almost every object on 

 which they alight, whether food or not. In feeding, as has 

 been shown already they frequently moisten soluble substances, 

 and often attempt to dissolve insoluble materials with vomit 

 and saliva, and even during feeding have been noticed to 

 deposit faeces. Recently 1 102 vomit marks, and 9 faecal deposits 

 were counted on an area six inches square of a cupboard window. 

 Plate XVIII, fig. I, is a photograph of part of this window 

 showing a row of faecal masses, probably deposited by one fly, 

 and several vomit marks. 



" One does not like to think that the fly now walking round 

 the edge of the cream jug was a short time ago regaling its 

 impartial palate on the choicest morsels in the dust-bin, ash-pit 

 or garbage-can, or on more indescribable filth." 



The house-fly is a diurnal species, resting during the night. 

 It loves shady places, and is not specially attracted to bright 

 windows. 



The activity of flies is much influenced by temperature, a 

 fall in the temperature often changing activity into stupor. 



At midsummer flies probably do not often live more than 

 two or three weeks, but accurate information on this point is 

 difficult to obtain apart from experimental conditions. In the 

 autumn they may be kept in captivity for several weeks. 

 Under natural conditions, however, in the autumn the majority 

 succumb to the attack of the fly fungus {Einpusa nmscce, see 

 Chapter xxill), but some linger on until the early winter months. 

 They do not disappear, however, altogether during the winter 

 months as popularly thought, but may be found in such places 

 as kitchens or bake-houses, where the temperature conditions are 

 favourable. Possibly some of them may remain dormant 

 throughout the winter in sheltered but cold situations. 



The blow-flies {C. crytJirocephala and C. vomitoria) and flesh 

 flies (5. caniarid) often enter rooms apparently attracted by 

 the presence of cold meat and similar substances, with the 

 object of depositing eggs. Like the house-fly, however, they 

 attempt to ico.^ on every article of diet. The green-bottles 



