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Transactions. 



the blue colour becomes replaced by yellowish, especially at one end. 

 Later the white embryo can easily be seen within the shell. After hatching, 

 the shell becomes filled with particles of white frass. The egg is easily 

 found, and the empty shell, which is strongly attached to the leaf, persists 

 long after the larva has left the mine and pupated, the shiny white shells 

 being quite conspicuous at the commencement of the galleries. 



Egg-laying. — This naturally takes place during those months in which 

 the imagos are to be found (see above). The ova are deposited singly, 

 invariably on the upper side of the leaf with the one exception of the 

 August-September brood mentioned below. The most favoured position 

 for the egg is alongside the midrib of the leaf, and the locality next in 

 favour is alongside one of the coarser veins or ribs. A number of eggs may 

 be found on any one leaf, but it is likely that these have been deposited 

 by several females. It has been noticed that in such cases the majority 

 of the eggs were laid on the basal half of the leaf. When the August- 

 September eggs are being laid the food-plant, 0. nitida, is sending out its 

 fresh spring buds, and on the hairy outer side (what will later be the 

 underside) of the bud leaves many of the ova of this moth are attached, 

 with peculiar consequences, as will be seen. 



The Mine. (Plate XL.) 



The mine is a narrow, usually more or less tortuous gallery, constructed 

 entirely under the upper cuticle of the leaf. The larva burrows directly 

 through the bottom of the egg into the leaf-substance ; and following this 

 there is no purple discoloration of the leaf in the egg area such as there is 

 in the case of N. fulva on the same food-plants. The gallery is not a long 

 one, its average length ranging; from 4 cm. to 6 cm. ; its course follows 

 the coarser ribs of the leaf, these and the midrib forming a bar to progress 

 across them. For this reason, and on account of the ova being usually 



Fju. 5. — Mines of N. ogygia in leaf of O. nitida. Natural size. 



deposited alongside the midrib of the leaf, most of the mines will be found 

 to be within the primary loops formed by the veins — i.e., those nearest 

 the centre of the leaf. -Towards the outer margin of the leaf neither the 

 midrib nor the coarser veins form very serious obstacles, and may be 

 crossed by the mines. The width of the mine increases very gradually, 

 and at its terminal portion is not more than 1-5 mm. The frass (sec 

 Plate XL) is black and coarsely granular, abundant, and occupies an almost 

 unbroken chain along the middle half or three-quarters of the gallery ; 

 it is entirely absent in the terminal half-centimetre of the mine ; it is 



