44 ! Fe'br\iary, 



prevail here as were present in the 2nd segment ; but whereas it was 

 often a delicate operation there to distinguish between the internal 

 organ and what was merely a staining of the skin, here the diagnosis 

 is made for us by the unmistakeable difference in the shape of the 

 marks. The large square-shaped spots are the surface markings ; 

 though to be strictly accurate, they are rather transversely oblong, 

 with the corners rounded, than square-shaped. Their size and deep 

 black colour make them extremely conspicuous, but curious to say, 

 they disappear with the last moult from all the segments save the 2nd, 

 and allow the other series of marks, or the nerve cord, which had 

 previously been concealed, to come into view. Both in their general 

 appearance and in the circumstance of being limited to the middle life 

 of the larva (for I should add they are not present from the first), 

 they remind one of the ventral spots in some of the Micropteryges. 

 Comparatively few species, however, seem to possess them. The only 

 ones I know of are the members of the angulifasciella group, subhi- 

 maculella, argentipedella, and if my memory serves me, qumquella, 

 but the last named does not occur here, and it is some years since I 

 was indebted to the kindness of Mr. Warren for the opportunity of 

 seeing it. The general tendency of the 2nd segment to exhibit pig- 

 mentation is not only shown by the retention of its ventral spot in 

 these cases, but also by the frequent presence of a grey mark in species 

 which never possessed the complete chain. For instance, it is very 

 distinct in glutinosee, serving to distinguish it from alnetella before 

 the two mines have acquired their distinctive characters, and it enables 

 one, at the same time, to draw the inference that the larva is lying 

 venter-up in the mine. 



The nerve-chain is known by the linear character of its links or 

 ganglia. Of its structure I need not speak, further than to observe, 

 that the three thoracic ganglia, and especially the 1st, are wider, that 

 is, more oval than the eight abdominal ones ; that all the eleven can 

 generally be counted by the aid of a good lens, though the 1st is 

 sometimes hidden by the ventral spot of segment 2 ; and that the 

 bands connecting them are, in some species at least, double in the ab- 

 dominal as well as the thoracic regions. Invisible in many species, 

 they are particularly so in those of a green colour— in fact, I cannot 

 call to mind a single bright green larva that shows even a trace of 

 them, so that it would seem that there is a sort of incompatibility be- 

 tween this colour and the development of pigmentation in the nerve 

 centres. Again, it is interesting to notice that the cephalic ganglia 

 may be plainly visible on the upper-side of segment 2, and yet no 



