A. M. Altson 193 



At the time of maturation, the mandibles are pale brown and gradu- 

 ally darken as the residual-yolk-mass is consumed, and harden to enable 

 the larva to commence its attack. 



In thirteen specific instances it took the young larva from three to 

 five days to consume the residual-yolk-mass. Very little of the vessel 

 contents is eaten, but apparently enough to clear a space for itself to 

 undergo an ecdysis; which was observed to occur between seven and ten 

 days after maturation. Shortly after settling down in the vessel pre- 

 paratory to moulting, the head capsule is exserted, and the thorax and 

 abdomen become slightly arched. 



Second Instar. After extricating itself from the first instar exuvium, 

 which splits primarily along the frontal and epicranial sutures and then 

 along the thorax, the larva rests to harden. 



About 24 hours later it commences to bore into the wood tissues. 



In the majority of cases observed, the young larva had eaten its way 

 through the vessel, into the tissues, at approximately right angles to its 

 original path, and had taken a downwards course for some distance 

 before again turning at right angles; it had then started boring in a 

 direction opposite to that in which it had originally begun travelHng. 



In the others, the larva had struck off to the left or right downwards, 

 the direction depending upon which outer margin of the piece of wood 

 the egg had been deposited in. In these cases the larva also turned again 

 after boring some distance down. 



In a few instances it was noticed that after biting through the vessel 

 in which it was hatched; it had come into an adjacent vessel, and had 

 turned into this and utihsed it for some distance until it had gradually 

 enlarged it and worked its way into the tissues surrounding the vessel. 



The foregoing observations are based upon the behaviour of second 

 instar larvae in small pieces of mahogany, of a size which enabled the 

 writer to find the eggs after each piece had been made accessible to 

 females for one night. 



The sizes of these pieces, which were split on all faces longitudinally 

 with the vessels, and cut transversely at the ends, ranged from one to two 

 inches in length by one-eighth to about three-eighths of an inch in width 

 and thickness. So that the larvae's movements were considerably confined. 



No doubt, in large pieces of wood such as boards, baulks, etc., the 

 larvae would not return in a direction opposite to that in which they had 

 originally travelled along the vessel — after once boring into the tissues — 

 unless they found themselves at the extreme edge or surface of the wood; 

 but would bore in the same direction, only in a lower plane. 



Ann. Biol, ix 13 



