FLIES FOUND IN HOUSES 39 



Flies of this family are greatly attracted to fruit and jam, and 

 are often found in great numbers round cider-presses and packing 

 houses and in orchards. Barrows (1907) tested the reaction of 

 these flies, particularly D. ainpelophila Loew., to substances com- 

 monly found in fermenting fruits, such as ethyl alcohol, acetic and 

 lactic acids, acetic ether and mixtures of them. " The intensity of 

 concentration was known in each, an important consideration in 

 such work. It was found that the optimum strength of ethyl 

 alcohol and acetic acid was 20 and 5 per cent, respectively. It 

 was further ascertained that cider vinegar, fermented cider and 

 California sherry contain alcohol and acetic acid in per cents, 

 very close to the optimum strength. By experiment it was next 

 determined that the sense of smell, by means of which the food 

 is found, is located in the terminal segment of the fly's antenna." 



The larva; of most species feed on decaying vegetation, but 

 " they are nearly all attracted to excreta, and some of them breed 

 in human excrement" (Howard, 1911, p. 252). Consequently 

 these small flies may at times carry dangerous bacteria and 

 contaminate foods. 



PsychodidcE. Owl midges or moth flies. 



Minute moth-like flies, very commonly found on windows in 

 houses. The wings are very large and broad in proportion to 

 the size of the body, and when the insect is at rest slope in 

 a roof-like manner. (PI. IX, fig. 2.) 



In the species illustrated the ground colour is dark grey with 

 lighter patches. Body and wings covered with long fine hairs.. 



Length. 2 "3 mm. ; span of wings 6 mm. 



Head. Eyes nearly meeting below vertex. There is a tuft of long white hairs below 



the antenna;, w-hich are as long as the body, and consist of twelve well-marked 



oval joints clothed with hair. 

 Thorax. Covered with greyish white hairs, especially at the sides. 

 Wings. With peculiar straight venation, covered with grey and black hairs arranged 



in double rows along the veins. The borders are also very hairy. 

 Legs. Clothed with black and white hairs arranged in bands. 

 Abdotnen. The segments are well marked and clothed with long hairs. 



Some of these flies of the genus Phlebotoimis occurring in 

 Southern Europe are blood-suckers and transmit a disease known 



