FLIES THAT FREQUENT HOUSES 



49 



THE BLUE-BOTTLE OR BLOW-FLIES 



Calliphora erythrocephala and Lucilia ccesar 



There are certain large flies known as "blue-bottles," 

 "green-bottles," or "blow-flies" that are found in houses, 

 especially during June and early summer. They may be 

 recognized by their large 

 size, buzzing noise, and 

 blue metallic colors. 



The common blow-fly, 

 C. erythrocephala, has a 

 bluish-black thorax and a 

 dark metallic blue abdo- 

 men (Fig. 19). The eggs 

 of this fly are usually laid 

 on fresh or decaying meat, 

 although they may be de- 

 posited in sores or wounds 

 of living animals. The fe- 

 male blow-fly seems capable of laying a large number 

 of eggs. Portchinsky records finding 450 to 600 eggs 

 from a single fly. Hewitt found that a generation of 

 these flies was produced in twenty-two to twenty-three 

 days. 



Normally, this blow-fly lives out-of-doors, but it often 

 enters houses in search of material upon which to deposit 

 its eggs and evidently also for shelter. It has been found 

 frequenting human feces and for this reason may be 

 suspected of bearing intestinal bacteria, thus making it 

 a fly to be dreaded. 



The other "blue-bottle" (L. ccesar) is smaller than the 



Fig. 19. — The blow-fly. (X 2.) 



