258 THE LIFE OF AN INSECT. 



velopment he watched with great interest. These 

 pupae belonged to a beautiful species of moth, 

 which has two broods in a year ; that is, it lays 

 eggs in May which become butterflies in July, 

 and then again lays eggs which become pupae in 

 August or September, but do not become butter- 

 flies until the following June. He was curious 

 to see whether this second brood, instead of 

 waiting for several months, would, like the first, 

 disclose its butterflies in a considerably shorter 

 time, now that it was exposed to the warmth of 

 the Conservatory. Such actually proved to be the 

 case ; and thus two generations of these butter- 

 flies were obtained in one year. Alluding to the 

 depredations of caterpillars, he quaintly remarks, 

 " This certainly is not a secret which appears very 

 profitable at present ; but who can tell whether 

 that which is useless to us to-day, may not pos- 

 sibly become of value to-morrow? Could we 

 discover some new species of larvae which would 

 supply us with as good a silk as that of the silk- 

 worm, and might be more easy to rear, but which 

 only produced one generation in each year, and if 

 it lived upon leaves which could be found all the 

 year through, we might avail ourselves of this 



