LATRINE FLY 193 



The Latrine Fly. Fannia scalaris Fab. 



This species, which, on account of its most common breeding 

 habits, may be called the Latrine-fly, is very C(jmmon both in 

 European countries and in North America. Owing to its general 

 similarity, it is often confused with the Lesser House-fly, Fannia 

 canicularis, but the chief differences have already been indicated. 



In the male the frontal triangle on tlic head is black and is 

 continued as a thin line to the vertex, being bordered on each 

 side by a silvery white stripe. The antennae and palps are black. 

 The thorax and scutellum are black and somewhat polished ; the 

 humeri are light-coloured. The abdomen is black, overspread 

 with bluish-grey, and has a darker median stripe from which 

 dark transverse bands arise, forming by their junction with the 

 median stripe black triangular markings. The legs are black 

 and the middle femur is swollen ventrally, bearing on its broader 

 side a gi-oup of brush-like bristles, as will be .seen from fig. 81. 

 The middle tibia is provided, as shown, with a distinct tubercle 

 near the distal end. 



The colouring of the female is more distinctly grey, with a 

 faint longitudinal striping on the thorax ; the transverse markings 

 on the abdomen are also indistinct. The head is grey with a wide 

 frons. 



F. scalaris is slightl}- larger than F. canicularis, measuring 

 up to 6 mm. in length. 



The habits of this species are somewhat similar to those of 

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

 the eggs and is commonly found breeding in human excrement. 

 It has been recorded breeding in human excrement by Schiner, 

 Taschenberg, Howard and Newstead, and I have also bred it 

 from this material in England and in Canada, both in privies 

 where the excrement was found in a semi-liquid condition and 

 on rubbish-tips or dumps, where it was mixed with ashes or 

 clinkers. Swammerdam figured what would appear to be the 

 larva of this species as breeding in human excrement. Taschen- 

 berg also refers to its breeding in mushrooms. In 1908 Dr David 

 Sharp submitted the larva of this species to me for examina- 

 tion. He had found it in rotting fungus in the New Forest 



H. H.-F. 13 



