57 



their being brought into existence ar- 

 rives, when there is plenty of food for 

 them. The young ones are small on their 

 being first hatched, but as we observed 

 before, they begin the work of destruc- 

 tion by marshalling themselves on the 

 young leaves of the trees, eating off the 

 epidermis, and destroying it altogether as 

 they advance. As long as they are in their 

 first skins they remain together, and are of 

 a deep black colour, but when they arrive 

 at about one-third of an inch in length, 

 they begin to change their skins, this 

 is done at three different times, which 

 I shall describe. When the time ap- 

 proaches in which they put off tlieir first 

 skin, they spin a web together, on which 

 they sit fast and remain quite motionless, 

 after which their heads are observed to 

 swell, and the old skin, w^hich is now be- 

 come too narrow, bursts, after whicli the 

 caterpillar a]}pears something larger, its 

 head and the })oints of its hairs are pale, 

 but in a few minutes change to a dark 

 colour, nearly black ; after this they begin 

 to look abroad for food ; the other chansr- 

 D 5 



