38 PHLEBOTOMUS [CH. 



on the flies, for on still warm nights they are found in large 

 numbers in houses. On the other hand, they rarely appear 

 when cool fresh breezes are blowing, in this respect resembling 

 the common midges of England. The chief breeding places 

 seem to be the crevices between rocks, in loose stone walls, 

 caves, also dark cellars, and especially on the sides of drains 

 kept moist by the occasional splashing of water. Unfortu- 

 nately, much work remains to be done on this subject, for 

 the task of finding the minute larvae or pupae is very difficult. 



Fig. 21. Phlehotomus papatasii, Scop. Female. 



and little is known about their habits. The difficulty of find- 

 ing the larvae is still further increased by their peculiar habit, 

 when exposed to light, of flicking themselves off the surface of 

 the object on which they are resting. The pupae are even 

 more difficult to detect, for not only are they very minute, 

 but closely resemble the colour of their surroundings. It is 

 therefore not surprising that so little is known about their 

 habits, in spite of the importance of this knowledge from a 

 prophylactic point of view. 



The flies are very unequally distributed even in regions 

 that seem to present the same conditions, such as an abundance 

 of stone walls for breeding places. Moreover, some houses are 

 visited much more frequently than others without any apparent 



