HABITS 85 



{L. ccEsar) seem to be greatly influenced by light (p. 25), but 

 are nevertheless frequently found in rooms, and then behave 

 like blow-flies. 



The cheese fly {P. casei) is attracted to cheese and fatty 

 substances in which it lay its eggs, and the fruit flies {DrosopJiila) 

 are frequently found about dishes containing fruit and jam. 



D. Hibernation. 



As has been stated in the last section, small numbers of 

 house-flies probably hibernate. " In the first warm days of 

 spring, they reappear in our houses invariably in those portions 

 of our dwellings which are kept at a relatively high temperature; 

 thus we get a marked domiciliary distribution or a preponderance 

 of flies in those parts where both heat and food are available " 

 (Newstead, 1909, p. 6). 



Several other species occasionally hibernate in houses. The 

 best known of these are the blow-flies, which remain hidden in 

 various situations and come out on warm and sunny days ; the 

 raven fly (J/, corvind), which frequently hibernates in country 

 houses, and the cluster fly (/". rndis). A plague of the latter 

 insects has been well described by Howard (191 1, p. 237). 

 " They were at once a terror to good house-keepers and a 

 constant surprise, since they were found in beds, in pillow slips, 

 under table covers, behind pictures, in wardrobes, and in all sorts 

 of places. In clean, dark bed-rooms seldom used, they would 

 form in large clusters about the ceilings.... They were stated to 

 be very sluggish — to crawl rather than to fly away when 

 disturbed. They were said to be found often in incredible 

 numbers under buildings, between the earth and floor." 



E. Habits after feeding. 



Observations on the functions of the proboscis, crop and 

 proventriculus, and the ways in which flies feed have been 

 quoted in previous chapters. Here it is only necessary to 

 consider the habits of flies after feeding on various materials. 



