154 THE BUTTERFLY VIVARIUM. 



taken from the garden as particularly fine speci- 

 mens, and added to those artificially reared. It is 

 very probable that one out of four or five so added 

 would exhibit the curious transformation about to 

 be described. The Caterpillar in question, not pre- 

 senting any appearance of an unusual character to 

 the inexperienced eye, will suspend itself for changing 

 in the usual manner ; but when the student is ex- 

 pecting the skin of the larva to be thrust off by the 

 expansion of the Chrysalis within, it is simply rent 

 or spread open, and a number of small cocoons of 

 yellow silk are seen attached to its inner surface. 

 Each of these cocoons contains a small oval Chry- 

 salis, from each of which in a few days (if the 

 Caterpillar was of the early brood) a small Fly will 

 issue, whose scientific name is Microgaster Olom- 

 meratns. Thus from the body of a single Caterpillar 

 issues a whole flight of little Flies, creatures belong- 

 ing to quite a distinct class of insects. This must 

 indeed have been an inexplicable surprise to a young 

 entomologist in his first season of experiments, and 

 one which would almost induce him to throw over 

 the discoveries of Swammerdam and Reaumur, and 

 return to the theories of spontaneous generation 

 — thus proved, as it seemed, under his own 

 observations. 



