I. TRÄGÅRDH, LEPIDOPTEROUS LEAF-MINERS. 



41 



If, however, we arrange them according to the degree of 

 reduction the maxillse ha ve undergone, we obtain the follow- 

 ing series: Gracilaria, Ornix, Lithocolletis and Phyllocnistis. 



In Gracilaria we notice the following features (fig.58). The 

 genae are narrow and of equal width throughout. The trian- 

 gulär plates, usually considered homologous with the sternite 

 of the 5th segment of the head, are small, triangulär and 

 placed far back, leaving in the middle of the ventral side a 

 large area occupied by the labium and the maxillse. In the 

 latter it is not possible to discern any articulation. As, 

 however, the stipes always ha ve 2 pairs of hairs, and we find 

 these in the basal portion of the maxillae, although far more 



Fig. 60. Head capsule of Ornix pomifoliella, lst instar, ventral aspect. X 155. 

 Fig. 61 . Ornix guttea, 1st instar. Top of maxilla, labium and mandibles, X 450. 



apart than is usually the case, and as all our experience 

 tends to show that the hairs are astonishingly conservative 

 features, we may safely conclude that the greater part con- 

 sists of the stipes. These widen gradually forward, and 

 their thin edge projects beyond the apodema, which is the 

 median margin of the genoe. On a level with the base of 

 the antennse they narrow down to a neck-shaped portion, 

 curving inwards and then outwards. The end of this is di- 

 vided into two narrow lobes, the median one of which is 

 again divided into two. All lobes carry a small, conical bristle 

 and we have no difficulty in recognizing in them the maxil- 

 lary palpus and lobus externus and internus, the narrow 

 portion which carries them being probably the palpiger. 



