HABITS OF THE LARVA OF BELLURA MELANOPYGA. IOI 



the mining habit and begins to burrow lengthwise down the 

 petiole. It is initiated when the larva locates either the midrib, 

 or the junction of the leaf with the petiole, and from this time the 

 feeding activities are confined almost entirely to the petiole. The 

 latter is usually reached in one of two ways: (i) the larva burrows 

 through the leaf substance or wanders on the surface until it 

 reaches the midrib, whereupon it bores into it, tunneling towards 

 the attachment of the petiole, or (2) the larva burrows or eats 

 through the substance of the leaf or wanders on the surface until 

 it reaches the attachment of the petiole where it then begins to 

 excavate. At about this time the larva has attained such a size 

 that mines can no longer be made but instead a broad slit in the 

 leaf is produced. This slit (Figs. 3-5) is usually a trifle wider 

 than the diameter of the larva producing it and almost invariably 

 extends directly towards the midrib or its junction with the 

 petiole. Sometimes a number of these slits are made before the 

 larva constructs one which reaches into the substance of the 

 midrib but all extend in the same general direction. If the midrib 

 is reached first the larva bores lengthwise into it and towards the 

 junction of the leaf with the petiole. Only very rarely were 

 larvae found boring in the opposite direction. The work in the 

 midrib is merely preparatory to the work in the petiole, being 

 only a means of getting into the upper end of the latter. It is not 

 possible at present to account for the ability of the larva to 

 recognize the position of the midrib or the petiole from any 

 position on the surface of the leaf, and to distinguish between the 

 apex of the midrib and the attachment of the petiole. 



As will be shown later active dissemination of the larvae begins 

 at the initiation of the petiole period. Many instances were 

 observed in which a larva had come to a new leaf and with sur- 

 prising exactness had gone directly to the junction of leaf and 

 petiole and had burrowed into it. Other similar instances were 

 observed in which the larva on reaching a new leaf had cut a 

 preliminary slit through the leaf leading directly to the top of 

 the petiole. This ability to work directly from the periphery 

 of a new leaf to the region of the petiole is especially marked in 

 larvae over 3 cm. in length. These facts were made apparent 

 many times by field experiments in which larvae 4 cm. in length 



