CH. XV.] SPECIES OF DIPTEROUS INSECTS. 223 



ther, from the immense number of young produced 

 from a single fly (and it is ascertained that the 

 Musca carnaria will produce 20,000 young), as well 

 as from their exceedingly rapid growth (scarcely a 

 fortnight ensuing between the birth of one genera- 

 tion and the deposition of young by the insects of 

 which it is composed), the production of a sufficient 

 number of individuals to fulfil the functions of the 

 species is amply ensured. 



It is to Reaumur that we are indebted for our 

 knowledge of the pecuharities above mentioned; 



Abdomen of the Blowfly opened, showing the spiral roll of 

 Larvse. 



and it is from his invaluable " Memoirs," that the 

 following figures, in illustration of the subject, are 

 derived. From his researches it appears that there 

 are two very distinct ways in Avhich these young 

 grubs are arranged in the body of the parent pre- 

 viously to their exclusion. In some species, inclu- 

 ding the MiLsca carnaria, these minute larvae (each of 

 which is enclosed in a distinct membrane of the 

 most delicate texture) are arranged side by side, and 



