A third e-pecies, commonly called Jie cluster fly {PoUenia nidis). 

 is a A'ery frequent visitant of houses, particularly in the spring and 

 fall. This fly is somewhat larger than the house fly, ^Yith a dark- 

 colored, smooth abdomen and a sprinkling of yellowish hairs. It is 

 not so active as the house ^j, and, particularly in the fall, is very 

 sluggish. At such times it may be picked up readily, and is very sub- 

 ject to the attacks of a fungus disease which causes it to die upon 

 Avindow panes surrounded by a whitish efflorescence. Occasionally 

 this fly occurs in houses in such numbers as to cause great annoyance, 

 but such occurrences are comparatively rare. 



A fourth species is another 

 stable fly known as Cyrto- 

 nevra stahulans, and a fifth, 

 rather commoner than the 

 last, is the so-called blue- 

 bottle fly {CallipJiora eri/- 

 tlir<>c('j>li<ila). This insect is 

 also called the blowfly or 

 meat fly, and breeds in de- 

 caying animal material. 

 Another species, about the 

 size of the bluebottle, which 

 breeds abundantly in cow 

 dung and is also foiuid in 

 houses, although usually in 

 less numbers than the oth- 

 ers, is also commonly called 

 the bluel)ottle or green-bot- 

 tle fly {Lucilki cu'sa)'). 



There is still another s]:)e- 

 cies, smaller than any of 

 those so far mentioned, 

 which is known to entomol- 

 ogists as Hoinaloniyia canicular'is^ sometimes called the small house 

 fly. It is distinguished from the ordinary house fly by its paler and 

 more j^ointed body and conical shape. The male, which is much 

 commoner than the female, has large pale patches at the base of the 

 abdomen, which are translucent. AVlien seen on a window jDane the 

 light shines through that part of the body. It is this species that is 

 largely responsible for the prevalent idea that flies grow after gaining 

 wings. Most people think that these little Homalomyias are the 

 young of the larger flies, which, of course, is distinctly not the case. 



Still another species, and this one is still smaller, is a small jet- 

 black fly known as Scenojnnus fenestralis^ which in fact has become 



[Cir. 35] 



Fig. 2.— The common house fly: a, ftill-grown hirva; 

 b, one of its anterii>r spiracles: c, antenna; </, liind end 

 of body showing anal spiracles: e, side view of head: 

 /, head from above: g, head of yonng larva; /;, eggs — all 

 enlarged (author's illustration). 



