Watt. — Leaf -mining Insects of New Zealand. 



461 



any incursions made by other insects, and also along one or both of the 

 sides of the midrib, this forming a barrier only in its basal three-quarters. 

 The gallery then follows a more or less tortuous course within these 

 boundaries ; if the leaf be large it will rarely cross earlier jiarts of its own 

 track, and will wander in a vermiform manner along one half of the leaf, 

 generally that half opposite the one on which the egg was laid ; in smaller 

 leaves almost the entire upper surface will be mined in a very compli- 

 cated manner, but there is never any tendency to blotch formation as in 

 P. 'panacitorsens. Loops may be thrown out from the straight central 

 portion of the gallery against the midrib, but never blind branches : this 

 is characteristic. The way in which the gallery closely follows the margin 

 of the leaf nearly all the way roimd was very characteristic of the Eo-mont 



Figs. 23, 24, 25. — Typical mines of P. pa7iacifinens in leaves of Nothopanax 

 arboreum. (Two-thirds natural size.) 



mines, but was not so constant in the Dunedin ones. Perhaps the chief 

 characteristic of the mine is the absence of blind branches. Frass is almost 

 negligible, black, very finely granular, and is irregularly distributed. As 

 a rule it is deposited at the margins of the mine, alternately on either side 

 m the early parts, but later is arranged in close curved lines, convex 

 forwards, transversely across the gallery. In the final stages it tends to 

 become somewhat fluid in character. 



The Cocoon. 

 The cocoon is constructed in the slightly expanded terminal part of the 

 mine, somewhat deeper in the leaf than the rest of the gallery. Its position 

 may be alongside the midrib, the outer margin, or one of the coarser veins 

 of the leaf. The small cylindrical structure of white silk pulls in the cuticle 

 of the leaf in its vicinity and causes the leaf here to become slightly 

 elevated, puckered, and infolded, affording it greater protection. A small, 

 thin, almost transparent white window is constructed in the upper surface 

 of the leaf at the end of the cocoon by the larva just prior to pupatioii. 

 Size, about 8 mm. by 3 mm. 



