DIPTERA. 413 



at it, turn to egg-shaped pupae, and come out as flies, in a few 

 days more ; or they remain unchanged through the winter, if 

 they have been hatched late in the summer. A smaller fly, of a 

 brilliant blue-green color, with black legs, also lays its eggs on 

 meat, but more often on dead animals in the fields. It seems 

 hardly to differ from the Musca (Lucilia) Cccsar of Europe. 

 The house-fly of this country has been supposed to be the same 

 as the European Musca domestical but I cannot satisfy myself 

 on this point for the want of specimens from Europe. It is pos- 

 sible that our sharp-biting stable-flies, the meat-flies, and the 

 house-fly, may really be distinct species from those which are 

 found in Europe. Our house-fly is the Musca Harjnjia, or Har- 

 py-fly, of my "Catalogue." It begins to appear in houses in 

 July, becomes exceedingly abundant in September, and does not 

 disappear till killed by cold weather. It is probable that, like 

 the domestic fly of Europe, it lays its eggs in dung, in which its 

 larvce live, and pass through their changes of form. The Amer- 

 icans are accused of carelessness in regard to flies, and apparent- 

 ly with some reason. But, if these filthy, dung-bred creatures 

 swarm in some houses, covering every article of food by day, and 

 absolutely blackening the walls by night, in others comparatively 

 few are found ; for the tidy house-keeper takes care not to leave 

 food of any kind standing about, uncovered, to entice them in, 

 and makes a business of driving out the intruders at least once a 

 day. If a plateful of strong green tea, well sweetened, be placed 

 in an outer apartment accessible to flies, they will taste of it, and 

 be killed thereby, as surely as by the most approved fly-poison. 

 In the first volume of " The Transactions of the Entomological 

 Society of London," Mr. Spence gives an account of a mode of 

 excluding flies from apartments, which has been tried with com- 

 plete success in England. It consists of netting, made of fine 

 worsted or thread, in large meshes, or of threads alone, half of 

 an inch or more apart, stretched across the windows. It appears 

 that the flies will not attempt to pass through the meshes, or be- 

 tween the threads, into a room which is lighted only on one side ; 

 but if there are windows on .another side of the room they will 

 then -fly through; such windows should therefore be darkened 

 with shutters or thick curtains. 



