OF GENERATION. 343 



vulgarin} about 3,000, the Coccus from 2,000 to 4,000. If even 

 these considerable multitudes are to be classed among the rare instances, 

 yet a posterity of a thousand individuals in one generation is very 

 common among insects. We find this number among the majority of 

 Nocluce ; Lyonet considers this number as usual in Cossus ligniperda. 

 Euprepia caja lays about 1,600. In the silkworm the average is about 

 500. Other orders are less fertile, for example, the Coleoplera ; in 

 these the average is fifty : many, as the Chrysomefce, lay more (viz., 

 Chrysomelce polygon?) ; others, for example, Meloe, Lyltu, which have 

 baccate ovaries, also lay many eggs, namely, from 600 to 800. The 

 burying beetle (Necrophorus vespillo) is said to lay only thirty eggs, 

 and the flea, according to Roesel, only twelve ; many Diptera, as the 

 gnats, some dozens; others, particularly flies, very few., from six to 

 eight : Musca meridiana, according to Reaumur, lays only two eggs, 

 but certainly not in the whole, but at one time. The Diptera pupipara, 

 the account of whose development we have given in the preceding 

 paragraph, always lays but one egg, or rather brings forth but one at a 

 time ; and it is the same with the Aphides, who bring forth a numerous 

 progeny, but only one at a time, at longer or shorter intervals, whereas 

 insects which lay eggs continue to lay until their entire stock is 

 exhausted. We may readily comprehend the incalculable number of 

 insects from this multitude of eggs laid by a single one. Reaumur 

 observed a Phalena from whose numerous eggs 350 living young ones 

 were developed ; many of them died as caterpillars, so that only sixty- 

 five females were found among those that passed through their several 

 metamorphoses ; but even this number were calculated to produce the 

 following year a posterity of 22,750, which in the succeeding one, by 

 the same calculation, would give a succession of 1,492,750 young ones. 

 A single Aphis likewise, by Reaumur's calculation, produces in the 

 fifth generation a succession of 5,904,000,000, and it is well known 

 that the great great grandmother still lays eggs when the ninth member 

 of her descendants is capable of re-production. 



