Milleb and Watt. — Study of New Zealand Entomolo 



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283 



Fig. 14. — Mouth- armature of larva, P. albiceps. 

 <i. anterior process : p. posterior process ; 

 ml, mid -lateral process. 



pigmented, Mack, excepting the mid-lateral processes, which are lighter 



in colour. The hooks are directly connected with the mouth, and are 



used horizontally to scoop the 



inner substance of the leaf. In 



all carnivorous larvae, on the 



other hand, the great hooks 



are utilized merely as a means 



of travelling, and are not in 



direct communication with the 



mouth. 



A day prior to pupating the 

 larva forsakes the upper surface 

 and commences burrowing against the lower cuticle of the leaf, scooping 

 out a chamber for itself. The following observations are of interest : Out 

 of a total of 659 mines observed, ninety-one larvae had hatched, mined, 

 and pupated in the upper portion of the leaf, while no less than 521 had 

 descended to the lower surface to pupate. Still more significant is the 

 fact that thirty-six that had been laid on the under-surface had remained 



to pupate there, while six had come to the 

 upper surface to mine but had descended 

 to the lower cuticle to pupate. Five only 

 hatched on the lower portion of the leaf 

 and pupated on the upper. This clearly 

 demonstrates the presence of some special 

 sense in the larvae unknown to us.* 



The pupa (fig. 15) is destitute of hairs 

 or bristles : is dark-brown : not elongate 

 and narrow, but moderately stout; com- 

 posed of 10 segments, exclusive of the 

 light-brown tubercles bearing the anterior 

 and posterior appendages. In most 

 healthy pupae the colour is light brown, 

 with a darker medio-dorsal line. The 

 hairs and limbs of the fly within can be 

 clearly distinguished a few days before 

 emergence. The dorsal surface is more 

 or less flat, the ventral slightly convex, 

 while the anterior end is rounded and 

 the posterior pointed when viewed dor- 

 sally. Anteriorly the dorsal and ventral lines run about parallel — 

 lateral view — but posteriorly the ventral line is distinctly upturned 

 toward the posterior procesess, which, unlike the anterior, arise toward 

 the dorsal line. When the pupa is at rest beneath the lower leaf- 



* Several experiments have been carried out since writing the above. Leaves of 

 the food plant containing nearly full-grown larvae burrowing beneath the upper cuticle 

 were placed the right and the wrong way up on damp blotting-paper in shallow glass 

 petri dishes. When the leaves were kept exposed to the ordinary light of the room the 

 larvae pupated in the lower portion of the leaf, whether that happened to be the natural 

 under-surface or not. In complete darkness they, almost without exception, pupated 

 on whatever surface they were burrowing at the commencement of the experiment, 

 oblivious of the fact that the leaves were in many cases the wrong way up. One niay 

 safely say, then, that these larvae are influenced by light, and pupate in that portion of 

 the leaf where they will get the most shade. How they are influenced by light remains 

 to be seen. 



Fig. 15. — Pupa of P. albiceps. 

 Fie;. 16. — Anterior process. 



