FLIES FOUND IN HOUSES 33 



Fannia {Hoinaloniyia) scalaris Fab. The latrine fly. 



This species very closely resembles the lesser house-fly, and 

 is probably often mistaken for it. "The abdomens of both 

 species are conical, but the basal segments of the abdomen of 

 F. canicularis are partially translucent and the abdomen of 

 F. scalaris is black overspread with bluish grey ; the mid-tibiai 

 of the latter species bear a distinct tubercle which is not found 

 in F. canicularis'' (Hewitt, IX, 1912, p. 162). (PI. VI, fig. 2.) 



Length. 6 mm. ; span of wings 12 mm. 



//t'ac/. In the <? the eyes almost meet, but in the ? are separated by an area equal 

 to one-third of the diameter of the head. The frontal stripe is dark brown and 

 the orbital margins and cheeks white. The antenna* are blackish grey, with non- 

 feathered arista. 



Thorax. Dark grey with indistinct darker longitudinal stripes in the cf . In the ? 

 the stripes are moderately distinct. The thorax and scutellum bear long bristles. 



Wings. Clear, and similar to those of F. catiiciilarts. 



Legs. Black. The middle femur is swollen ventrally, and bears on its broader side 

 a group of brush-like bristles. The middle tibia bears a distinct tubercle. (Fig. 

 16.) 



Abdomen. In the <f it is very dark and has a darker median longitudinal band. In 

 the ? it is almost uniform dark brown. Yellow transparent patches are not 

 present in either sex. 



"The habits of this species are very similar to those of 

 F. canicularis, but it prefers excrementous matter as a nidus for 

 the eggs and is very commonly found breeding in human 

 excrement." The larvae are often found in privies when the 

 excrement is in a semi-liquid condition and on rubbish tips when 

 it is mixed with ashes and clinker. They have also been found 

 in mushrooms and in rotting fungus. Occasionally they are the 

 cause of intestinal myiasis in man (Chapter XXIl). 



The eggs are white and cylindrically oval. 



"The lanja of this species has a general resemblance to that of F. canicularis, 

 but a closer examination will reveal very marked differences and a number of 

 distinguishing characters. In shape it is very similar to the larva of F. canicularis, 

 being compressed dorso-ventrally. The appendages or processes, however, are very 

 different. The pair of antenna-like processes at the anterior and upper edge of the 

 prothoracic (second) segment are much shorter than those of F. canicularis, as will 

 be seen from the figure (15), where they are shown dorsal to the oral lobes. On the 

 dorsal side of the larva, from segment III to segment XI, is a series of nine pairs of 

 short and somewhat thick processes of a very spiny character ; the first two pairs 

 being little more than spinous tubercles. As the processes of the third segment differ 

 from the succeeding segment, they may be mentioned separately. There is a pair of 



G.-S. _1 



