ORDER DIPTERA: SCHIZOPHORA: THE MUSCOIDEA 151 



, /Scutum longitudinally striped Chrysomyia. 



I Scutum not longitudinally striped = 4. 



j Thorax and abdomen metallic green or bluish-green = Lucilia. 

 J Thorax and abdomen more brassy green or purplish-blue, the 

 I posterior margin of some of the abdominal segments blackish 

 V = Pycnosoma. 



I'Eyes wide apart in both sexes ; 2nd abdominal segment of 



female more than half the total length of the abdomen 



= Auchmeromyia. 

 I Eyes of male close-set ; 2nd abdominal segment of female not 



inordinately long = Cordylobia. 



Genus MUSCA. 



The species of this cosmopolitan genus are of smallish 

 size and dull colour — the thorax being blackish-grey and 

 the abdomen yellowish. The arista is feathered both 

 dorsally and ventrally. The proboscis is soft and retractile 

 and ends in large fleshy labella. The 4th longitudinal vein 

 bends forwards at an abrupt angle so as nearly to close the 

 1st posterior cell (Fig. 5). There is no tuft or comb of 

 bristles on the hypopleura, and no large bristle on the inner 

 surface of the tibiae of the middle legs. 



Musca domestica, L., the common house-fly, is a species 

 which is found in all parts of the world. The head is dark, 

 with a velvet-black frontal stripe. The scutum is dusted 

 with grey and marked sometimes rather indistinctly with 

 four equidistant black stripes of equal breadth. The 

 abdomen is yellow, with a median dark stripe and a dark 

 tip. In the male the eyes are set close together, in the 

 female they are wide apart. 



In very hot countries the house-fly has no particular 

 season and breeds more or less all the year round. In 

 colder countries it is abundant during the summer and 

 autumn, but — except for a few individuals that survive in 

 sheltered spots — dies out with the approach of winter. The 

 survivors of the winter, as well as new individuals that 

 emerge from pupae which have hibernated, soon increase 

 their kind as the weather becomes warmer. 



The habits of the house-fly are only too well known, and 

 the malign influence of this insect as an infective agent has 

 already been considered (p. 32). 



