40 FLIES FOUND IN HOUSES 



as "Three-day fever," but the species found in this country are 

 non-biting flies. Newstead (1907, p. 22) states that in Liverpool 

 the larva of P. pJialcEuoides " was common in human faeces and 

 many examples of the flies were bred from this material. It is 

 also common in putrid sewage matter." 



The flies are common in houses from March onwards, and 

 judging from their habits may occasionally carry disease pro- 

 ducing bacteria. 



Scenopinus fenestralis L. The window fly. 



This is a long, narrow, black fly with a hump-backed appear- 

 ance. The abdomen is relatively very long and flattened, and 

 shows well-marked segments. It is often found on windows, 

 especially in out-houses, and is not very active. (PI. IX, fig. 3.) 



Lettgth. 6 mm. ; span of wings lo mm. 



Head. Semicircular, and well separated from thorax. The frons and vertex are almost 

 flush with the eyes, or so slightly sunk that the eyes cannot be termed bulging. The 

 eyes in the J are almost touching, in the ? separated by an area equal to one- 

 fifth the width of the head. Cheeks and face, which is very broad but short, are 

 quite bare, and very dark grey in colour. Antennae are three jointed, and close 

 together at the base. The basal joints are short, but the third joint is elongated 

 and bent downwards and bears no distinct arista. 



Thorax. Dull black, almost shagreened, and has no bristles. It is flattened on the 

 surface, but the insect appears hump-backed because the head is depressed. 



Wings. Clear, but slightly yellow, with peculiar simple venation. Squama small. 

 Hal teres very long and with an oval knobbed termination, which is very variable 

 in colour "being sometimes all clear white, but often white on the under side of 

 the knob " or dark grey. 



Legs. Yellowish, sometimes with dark markings. The terminal joints of the tarsus 

 dark. 



Abdomen. Shining black and flattened, with seven well-marked segments, each of 

 which has a transverse channel across its middle. The second segment bears 

 peculiar oval pitted areas. Ovipositor in ? concealed. 



' ' The larva is long, white, and snake-like in shape with a dark head. It apparently 

 has many segments to the body, since each of the abdominal segments is divided by a 

 strong constriction" (Howard, 191 1, p. 260). 



" The larva was at one time supposed to feed on stable 

 clothing and old carpets, especially when thrown into a heap 

 and neglected, whence the perfect insect obtained the name of 

 'carpet fly.' It is now however known to be predaceous and 

 to feed on the larva; of the clothes moth {Tinea pcllionella) or of 



