270 



ECONOMIC ENTOMOLOGY 



C. Mesonotum flattened behind the transverse suture; posterior dor- 

 socentral and acrostichal bristles inconstant and unequally 

 developed. — Phormia. 

 CC. Mesonotum not flattened behind the transverse suture; posterior 

 dorsocentral and acrostichal bristles well developed and constant. 

 D. Cheeks hairy; third longitudinal vein {Ri^b) spinulose at 

 base only. — Calliphora. 

 DD. Cheeks bare; third longitudinal vein (R4+5) spinulose.— 

 Lucilia. 



.Trans verse sutur ,Post alar callus 



Propleura- 



Front coxa -^ 



Haltere 



Hind coxa 



Middle coxa- 



Fig. 172 — ^Lateral view of the thorax of a muscoidean fly, with designations of 

 the parts commonly used in taxonomic work. {After Riley and Johannsen.) 



House-fly {Musca domestica Linn.). — A cosmopolitan insect 

 dangerous to human life. A carrier for typhoid fever, tuberculosis, 

 dysentery and other diseases (Fig. 173). 



Adult. — A two-winged fly with four black hnes on back of thorax; 

 bristle of antennae feathered; vein ending near tip of wing distinctly 

 elbowed; no bristles on abdomen except at the tip. Mouth-parts used 

 for sucking not for piercing, retractile; mouth-parts and feet specially 

 adapted for carrying micro-organisms. Each foot with two claws and 

 two sticky pads. Egg-laying begins 10-14 days after adult emerges 

 from puparium (Fig. 174). 



Eggs. — Minute, glistening white, long ovoid, }^ inch long. Laid in 

 irregular small clusters. Each female lays about 120 eggs at a time 



