184 HABITATIONS OP ANIMALS. 



sufficient space to turn itself in the cell, which is almost entire- 

 ly filled with the pappy substance formerly mentioned. But, 

 as this substance is gradually devoured by the worm, the space 

 in the cell necessarily enlarges in proportion to the growth and 

 magnitude of the animal. 



We are informed by M. de Reaumur, that M. Pitot furnished 

 him with a piece of wood, not exceeding an inch and a half in 

 diameter, which contained the cells of a wood-piercing bee. 

 He cut off as much of the wood as was sufficient to expose 

 two of the cells to view, in each of which was a worm. The 

 aperture he had made, to prevent the injuries of the air, he 

 closed, by pasting on a bit of glass. The cells were then 

 almost entirely filled with paste. The two worms were ex- 

 ceedingly small, and, of course, occupied but little space 

 between the walls of the cells and the mass of paste. As the 

 animals increased in size, the paste daily diminished. He 

 began to observe them on the 12th day of June ; and, on the 

 27th of the same month, the paste in each cell was nearly 

 consumed, and the worm, folded in two, occupied the greater 

 part of its habitation. On the 2d of July, the provisions of 

 both worms were entirely exhausted ; and, besides the worms 

 themselves, there remained in the cells only a few small, black, 

 oblong grains of excrement. The five or six following days 

 they fasted, which seemed to be a necessary abstinence, dur- 

 ing which they were greatly agitated. They often bended 

 their bodies, and elevated and depressed their heads. These 

 movements were preparatory to the great change the animals 

 were about to undergo. Between the 7th and 8th of the same 

 month, they threw off their skins, and were metamorphosed 

 into nymphs. On the 30th of July, these nymphs were trans- 

 formed into flies similar to their parents. In a range of cells, 

 the worms are of different ages, and, of course, of different 

 sizes. Those in the lower cells are older than those in the 

 superior ; because, after the bee has filled with paste and in- 

 closed its first cell, a considerable time is requisite to collect 

 provisions, and to form partitions for every successive and 

 superior cell. The former, therefore, must be transformed 

 into nymphs and flies before the latter. These circumstances 

 are apparently foreseen by the common mother ; for, if the un- 

 dermost worm, which is oldest, and soonest transformed, were 

 to force its way upward, which it could easily do, it would 

 not only disturb, but infallibly destroy, all those lodged in the 

 superior cells. But nature has wisely prevented this devas 

 tation ; for the head of the nymph, and consequently of the 



