Watt. — Leaf-mining I //sect* of New Zealand. 213 



Distribution. 



I have found this moth in Wellington and in Dunedin, where it is com 

 mon. Larvae were found in May, July, August, November, and December. 

 Mevrick records one specimen from Christchurch, in March. 



Food-phi nl. 

 Senecio bellidioides. It is usually only the lower leaves that are attacked. 



The Ovum and Egg-laying. 



The egg is most inconspicuous. It is, however, like all the other 

 Nepticulid eggs, relatively large ; oval, wafer-like, domed above, and rather 

 wider at the micropylar end. Colour pale greenish-yellow. Laid singly 

 and well attached to the under-surface of the leaf, usually against one of 

 the coarser veins, but otherwise in no fixed position. The shell is shiny, 

 unsculptured, transparent, and extremely fragile. After the hatching of 

 the larva it crumples up, rarely persisting long at the end of the mine. 

 Average dimensions are 0-30 mm. by 0-20 mm. Laid singly, often a number 

 on one leaf. 



The Mine. (Plate XLII.) 



This is a simple, narrow, exceptionally tortuous gallery, more closely 

 applied to the upper than to the lower surface of the leaf. It is not till 

 about half-way through the larval stage that the mine becomes at all 

 conspicuous. In the earlier half of the mine the larva may cross its tracks 

 time and again, and those of neighbours also if these happen to be in the 

 way. Viewed under the microscope by transmitted light this early part of 

 the mine is a beautiful object. On the upper surface of the leaf it has a 

 silvery appearance when held in the light, otherwise is greyish in colour. 

 A number of mines may be constructed in a single leaf and the entire 

 leaf-substance consumed. In the last 2 cm. of the mine the gallery is 



Fig. 11. — Mine of X. tricentra in leaf of 

 S. bellidioides. Natural size. 



considerably widened, its edges scalloped and irregular, and owing to its 

 tortuousness this part frequently resembles a blotch. The frass is black, 

 fairly copious, and occupies a more or less unbroken central line ; it is 

 homogeneous in consistency, and rests on the floor of the mine. The 

 midrib of the leaf is a barrier in the early stages, but the final part of the 

 gallery frequently crosses it. Average length of the mine, 3 in. to 4 in. ; 

 final width, 2 mm. to 4 mm. The larva makes its exit through the upper 

 cuticle. I have rarely found the mine more than 12 in. to 18 in. from the 

 ground. In one specimen under observation the final 2 cm. of the gallery 

 were mined in four davs. 



