46 I February, 



that the light must be largely robbed of its power to produce pigmen- 

 tation in the former class, but remains unaffected as regards this 

 property in the latter class. 



Position also seems to be at the bottom of the ventral surface 

 markings. All the species that possess them lie venter up in the mine, 

 so do the Micropteryges, and so also do certain leaf-mining beetles that 

 have on the under-side of their thoracic segments conspicuous black 

 marks, very similar to those of the Lepidopterous larvae. 



The Intestinal Canal. — The feature here is the colour, which 

 may be red, yellow, or green in various shades. Frequently the fore 

 part is of a different colour to the hind part. In anomalella and 

 assimilella, for instance, the canal is green in front and yellow behind. 

 Occasionally it is so like in tint to the rest of the body, that its de- 

 monstration is next to impossible, but usually it stands out conspi- 

 cuously — its vivid green colour in several of the birch-feeders is very 

 striking — and may come in to help us at a pinch. In collecting the 

 mines of pyri, I commonly find myself taking the red intestinal canal 

 as the first critical step in separating it from oxyacanthella, which is 

 equally, if not more, common in the pear leaves, but has a yellowish 

 canal. The colour does not, of course, reside in the canal itself, but 

 in the contained food, which has been altered and discoloured by the 

 secretions.- And it is certainly curious that we should find, in such an 

 out of the way quarter as the secretions of the intestines, good dis- 

 tinguishing characters ; for since the food is the same, the difference 

 in the colour must be due to a difference in the secretions. 



The Paik of Beown or Black Lines at the Hindee End of 

 THE Body. — These again are internal organs, which I take to be the 

 kidneys. They are situated one on each side the intestinal canal, and 

 are best seen from the ventral surface. Under the microscope each ia 

 resolved into a long wavy or tortuous tube, bent upon itself in such 

 a way that the two ends lie close together at the anal extremity. I 

 first noticed them in distinguenda, where they can be seen very plainly, 

 even when the larva is in situ. They are besides quite discoverable in 

 some others, but I am inclined to think only in such as show an excess 

 of pigmentation somewhere else, as in the head or nervous system. 



I will now pass to a part of my subject more interesting, perhaps, 

 to the generality of readers, and shall hope to show how confidently 

 certain species, not unlike in mine and larva, and feeding on the same 

 kind of plant, can be distinguished from each other by attention to 



