6 BUTTERFLIES 



A butterfly lays an egg upon a leaf. Some days later 

 the egg hatches into a larva, which is the technical 

 name for the second stage of an insect's life. In the case 

 of the butterfly we call this larva a caterpillar. The little 

 caterpillar is likely to take its first meal by eating the 

 empty egg shell. This is a curious habit, and a really 

 satisfactory explanation of it seems not to have been made. 

 Its next meal is likely to be taken from the green tissues of 

 the leaf, commonly the green outer surface only being 

 eaten at this time. The future meals are also taken from 

 the leaf, more and more being eaten as the larva gets 

 older. 



After a few days of this feeding upon the leaf tissues the 

 little caterpillar becomes so crowded within the skin with 

 which it was born that it is necessary to have a larger one. 

 So a new skin begins to form beneath the first one. Con- 

 sequently the latter splits open in a straight line part way 

 down the middle of the back just behind the head. Then 

 the new head covering is withdrawn from the old one and 

 the caterpillar wriggles its way out of the split skin and 

 finds itself clothed in a new one. At first all of the tissues 

 of the new skin are soft and pliable and they easily take on 

 a larger size as the body of the caterpillar expands. A 

 little later these tissues become hardened and no further 

 expansion is possible. 



This process of skin-shedding is called moulting. The 

 cast skin is often called the exuviae. The period of the 

 caterpillar's life between the hatching from the egg and 

 this moult is often called a stage or instar — that is, the 

 caterpillar up to the time of this moult is living in the first 

 caterpillar stage or instar. 



During the actual moulting the caterpillar is quite 



