I. TRÄGÅRDH, LEPIDOPTEROTJS LEAF-MINERS. 29 



top, where a small incision exists. The basal half of the median 

 edge is provided with 5 — 6 fringed lobes, directed backwards. 



Phyllocnistis (fig. 45) is the last in this series, the deve- 

 lopment of the median blade far surpassing anything met 

 with in the other leaf-miners. One tooth still remains exte- 

 riorly, but the proximal half of its inner edge is covered by 

 the edge of the blade which has increased enormously in 

 size, being a thin blade with rounded, finely dentate edge. 



All that remains of the atrophied teeth, are some narrow 

 thiekened ridges. 



Summary. 



The modification of the mandibles seems to have taken 

 the following course. 



At the flattening of the head-capsule the mandibles also 

 became dorso-ventrally compressed; this resulted in the upper 

 half of the edge becoming more horizontal, and the ventral 

 half being curved inwards so as to lie below the lateral margin 

 of the upper part (figs. 38 — 39); at the same time the number 

 of teeth decreased, and probably the reduction began at both 

 ends, the uppermost tooth being fused with the anterior part 

 of the blade, while the ventral one become atrophied. This 

 stage is represented by Eriocrania and Tischeria which, how- 

 ever, differ, amongst other things, in one respect: in the 

 former a line connecting the tips of the dorsal teeth forms 

 an even curve with the edge of the blade; in the latter it 

 forms a straight line. 



This latter feature we notice also in Nepticula (fig. 40), 

 which is more primitive than the two preceding forms as to 

 the number of teeth. In Nepticula the 4 dorsal teeth lie in 

 a perfectly horizontal plane, and a line connecting their top 

 is perfectly straight, a feature brought about by their suc- 

 cessive decrease in size backwards. 



In Cemiostoma (fig. 41) this is still more marked, the line 

 connecting the top of the teeth being nearly in line with 

 the inner margin. 



The reason for this modification of the dentate edge as 

 compared with the shape of an external feeder seems to be 

 the difference existing between the mode of making use of the 



