Watt. — Leaf-mining Insects of Xew Zealand. 217 



mine on the upper surface of the leaf, and when the under-cuticle is 

 stripped off the mine gives it the honeycomb appearance. The preliminary 

 gallery often becomes absorbed into the blotch. The larger leaves may 

 contain a considerable number of mines ; I have found from twenty-six to 

 thirty on one leaf of 0. nitida. They occur in any part of the leaf, but the 

 majority in the outer portions. Leaves on all parts of the tree are equally 

 attacked. Neighbouring mines sometimes coalesce and become continuous 

 with one another. The frass is black and granular, and fairly plentiful 

 in the blotch, where it occupies the central two-thirds, being packed into 

 the excavated cell-spaces in the roof of the mine. Many of these cells are 

 entirely emptied of their contents by the larva, and the upper cuticle soon 



Fig. 13. — Mine of N. fulva in 0. nitida. Natural size. 



dries and becomes white externally. As the blotch enlarges, more of these 

 minute dots appear, closer together and more numerous in the central 

 portion of the mine. On the under-surface the blotch can be made out 

 more clearly, owing to the detachment and consequent looseness of the 

 cuticle over the part. In mines still tenanted by the larva the under- 

 surface is more or less bulged, and is slightly lighter in colour than the rest 

 of the leaf. When full-fed the larva eats a small semicircular outlet at the 

 margin of the blotch, through the lower cuticle, and descends to the ground 

 to pupate. The mine is not conspicuous till after the larva has left it, 

 when the part of the leaf affected becomes dead and shows in violent 

 contrast to the rest. 



The Larva. 



Length when full-grown, about 5 mm. Ground-colour pale green ; 

 central marking dark olive-green in its first half, darker in its caudal half. 

 Head pale greyish-brown ; darker reddish-brown sutural lines ; almost 

 acutely triangular in shape ; retractile. Cephalic ganglia and ventral chain 

 not observed. Segments well rounded, moniliform ; last three abdominal 

 segments extended, the tenth directed dorsally with narrow dark dorso- 

 lateral fines. Setae fine, fairly long. Body covered with a minute pile. 

 Saetal plan has been left for a future paper. Fleshy protuberances take 

 the place of prolegs. The larva mines dorsum uppermost. 



The Cocoon. 



This is constructed outside the mine amongst dead foliage at the foot 

 of the food-plant, The colour of the cocoon blends with that of its 

 surroundings and makes it most difficult to find. In the breeding- jars the 

 cocoons are always constructed between two fairly closely applied surfaces 

 in the darkest corners at the bottom of the jar, and they are fairly firmly 

 attached. The construction of the cocoon usually occupies about two 



