HOUSE FLIES AND BLUEBOTTLES 207 



is sure to be a great attraction. It also frequents 

 excrementitious matters in large numbers. It is as prolific 

 as the bluebottles, laying from 300 to 600 eggs, and, 

 like them, is in its larval condition essentially a carrion- 

 feeder. That carrion is its most natural food has been 

 decisively shown by the experiments of M. Portchinski, 

 a Russian entomologist, who placed eggs of three 

 different species of flies on each of three different food 

 substances, and carefully watched the results. The 

 species experimented upon were the present insect, one 

 of the bluebottles (C. eri/throcephala), and one of the 

 flesh-flies allied to the Sarcophaga already mentioned ; 

 and the foodstuffs were meat, cattle-dung, and decaying 

 mushrooms. The eggs soon hatched, and in all three 

 cases the maggots derived from those that had been 

 placed on the meat throve rapidly, and soon completed 

 their metamorphoses ; while all the rest grew but slowly, 

 and finally perished, with the exception of one batch, 

 viz., those of L. Ccesar, which had fed on the cattle- 

 dung; these, however, grew much more slowly than 

 those of the same species that had been fed on the meat ; 

 still they survived, and finally completed their meta- 

 morphoses. All that had been placed on the rotting 

 fungus died without exception. Carrion, therefore, is 

 the natural food of the larvae of the greenbottle, though 

 they will subsist on excrement, and those of the blue- 

 bottles are still more emphatically carnivorous. 



Though the greenbottles and bluebottles are so diffe- 

 rent in appearance as perfect insects, their larvae are 

 very similar, and in fact, as Sir John Lubbock has 

 pointed out, the form of a larva is dependent not only 

 upon the type of insect it is destined to produce, but also 

 upon its environment, so that those which live under 

 similar conditions may be expected, for that reason, to 



