32 FLIES FOUND IN HOUSES 



the prothoracic segment (segment II) and slightly increasing in size posteriorly. 

 A latero-dorsal series often pairs of processes which commences on segment III and 

 is continued to the posterior end of the body. A latero-ventral series, which com- 

 mences on segment III and is continued posteriorly. These flagelliform processes are 

 spiniferous, the spines being well developed at the bases of the processes and gradually 

 decreasing in size distally. The twelfth or anal segment is provided with three pairs 

 of these processes of unequal size ; the anterior pair is the longest on the body and the 

 intermediate pair is shorter. 



" There is a series of pairs of small, almost sessile branched appendages near and 

 slightly posterior to the bases of the latero-dorsal appendages. Each of these processes 

 has three or four branches, and they carry a small nucleiform organ, which Chevril 

 (1909) has also described. 



" On the ventral surface of the body and extending posteriorly from segment III 

 there is to be found a series of pairs of small spiniferous papillce. Between these there 

 is on each segment a transverse row of four groups of spines. 



" The anterior, or prothoracic spiracular processes have usually seven finger-like 

 lobes, though the number may vary from five to eight, and between the second and third 

 lobes there appears to be a small stigmatic organ. The posterior spiracular processes 

 have a tri-lobed appearance, but a close examination reveals their four-lobed character ; 

 a stigmatic orifice is situated at the extremity of each lobe. 



" The spiny character of the flagelliform appendages and body of the larva cause 

 particles of dirt to adhere readily to the bodies and appendages of the larvae. In con- 

 sequence the larvse have a dirty appearance and their external features are hidden by 

 the accumulated particles of dirt and filth adhering to them." 



" In changing into i\\e pupa, the cephalic region is retracted and the length of the 

 larva is thereby decreased. The larval skin, with its covering of dirt particles, forms 

 the co-arctate pupal case" (Hewitt, ix, 191 2). 



Breeding habits. " The breeding habits of this species are 

 somewhat similar to those of the house-fly, M. doniestica. The 

 larvae breed in decaying and fermenting vegetable and animal 

 matter and also in excrementous matter." They have also been 

 found in caterpillars, snails, old cheese, humble-bees' nests, and 

 pigeon nests, and on sugar beet and stalks of rape. They are 

 also not infrequently found in rotting grass. Occasionally they 

 cause intestinal myiasis in man (Chapter XXIl). 



"The larval period may extend over a week or it may last 

 for three or four weeks, if the substances in which the larvae are 

 feeding become rather dry." " The pupal stage extends over a 

 period of seven to twenty-one days or longer " and it is not 

 unlikely that the winter is passed in the pupal state. 



The larval stages may be found between May and October. 



