256 E. P. Stebbing — Life-history of Arbela tetraonis. No. 4, 



ity amongst the young larvae. The foliage of the Casuarina is very thin 

 and open and a caterpillar feeding in the open on the bark would be 

 very visible to bird and other depredators. It is, therefore, within the 

 bounds of probability that the caterpillars suffer heavily in this manner 

 in early life and that the grub has developed the habit of living in a 

 protective tunnel to safeguard itself from these attacks. During the 

 whole period it spends upon the trunk of the tree the larva feeds upon 

 the bark eating this latter away either in thin irregular-shaped patches 

 in places adjacent to its covered gallery or gnawing it right through down 

 to the wood below under the shelter given it by the covered way itself. In 

 this way the tree is at times very nearly girdled, and if a number of 

 larva? are working close together the result is probably the death of the 

 tree. Some trees seemed to be more preferred than others, several moths 

 resorting to them to oviposit. In such cases it often happens that one 

 or more of the covered ways made by the larvae developing from the eggs 

 meet at a kind of junction and a large mass of excrement and silk 

 forms a great bulge on the tree from which, if the moths have flown, 

 several empty pupal cases may be seen protruding quite close to one 

 another. When full fed the larvae returns down its covered way until 

 it has reached to about the centre and then bores horizontally into the 

 tree, going deep to the centre of the heart wood. This tunnel is kept 

 quite clean all the wood particles being ejected from it. When it has 

 arrived there after making a tunnel which may be as long as six or 

 more inches though in smaller trees it is considerably less, it slightly 

 enlarges the chamber, turns round in it and pupates. This tunnel in 

 the wood is only bored by the larva for pupating purposes. It does 

 not ramify about in the wood as would be the case if the grub were 

 feeding in the wood. 



From the periods at which both larvae pupae and moths have been 



found it is probable that the time passed as a pupa is short, probably 



•a month at most. When the moth is nearly ready to emerge the pupa 



projects itself along the tuunel by wriggling forward with the help 



of the rows of spines with which its outer covering is garnished. On 



reaching the end of the tunnel it forces its way through the covered way 



from the outer surface of which it projects for about one-fourth of its 



length. The case then splits down anteriorly and the moth crawls out. 



These empty pupal cases found projecting in this manner from the covered 



ways enable a period to be roughly fixed for the term of pupation. 



Under the action of the monsoon rain they soon get soaked and sodden 



and fall off the tree, and it is thus certain that but a few weeks are 



passed by the insect in this quiescent stage of its existence. 



The points which still remain uncertain are the exact length of 



