190 THE LESSER HOUSE-FLY AND THE LATRINE-FLY 



the nest of the humble bee, Bombus terrestris, and Schiner 

 observed them in the bottom of a b(jx in which a dormouse 

 had been kept. Taschenberg also records the larvae as being 

 found in snails, in old cheese and in pigeon-nests ; he reared the 

 flies from sugar-beet, and Brischke found the larvae in the stalks 

 of rape. I have found them commonly in human excrement and 

 in a variety of decaying vegetable substances, even in rotting 

 grass {cf. Stomoxys). In England they may be found in the 

 larval stages from May to October. Howard has reared them 

 from human excrement during the same period in the United 

 States, and in Canada I have observed the same period for the 

 occun'ence of the larval stages. Larvae of F. canicularis were 

 found by Carter and Blacklock (1913) in a case of external 

 myasis in a monkey {C'ercopithecus callitrichus). They Avere 

 removed, together with the larvae of Muscina stabulans and 

 Calliphora erythrocepJiala, from the nasal and facial region and 

 the right side of the body near the gi'oin, but it is probable, as 

 these authors point out, that they may have been derived from- 

 an external source. The eggs are white and cylindrically oval. 



The larvae of F. canicularis (fig. 83) is wholly different from 

 that of M. domestica, its body being provided with a number of 

 appendages or spiniferous processes. These are arranged in three 

 pairs of longitudinal series, and there are in addition two pairs 

 of series of smaller processes. 



The body is compressed dorso-ventrally, and the surface is 

 roughened in character and in places spiniferous. It consists of 

 twelve segments, of which the first, or pseudocephalic segment, 

 is often withdrawn into the second or prothoracic segment, as 

 shown in the figure. The posterior end of the body is very 

 obliquely truncate. The full-gi"own larva measures 5 to 6 mm. 

 in length. The three series of pairs of spiniferous flagelliform 

 processes, or appendages, are arranged as follows : A dorsal series 

 consisting of ten pairs of processes, commencing with an antenna- 

 like pair of processes at the anterior border of the prothoracic 

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

 A latero-dorsal series of ten pairs of processes which commence 

 on segment III and is continued to the posterior end of the 

 body. A latero- ventral series which commences on segment III 



