136 fMay, 



I have only met with one instance where, the mine being on the upper-8ide, the 

 blotch ran across instead of with the rib ; whilst two or three times I have found a 

 mine on the under-side of the leaf, which, no doubt, belonged to this insect, though 

 the fact could not positively be ascertained, as in each instance the larva died. 



Now, I find on birch a larva, which in its habits is the very antithesis of the 

 one I have been describing, tlie rule in the one being the exception in the other, and 

 vice versa. The mine (a gallery and small blotch) is on the under-side of the birch 

 leaf, very rarely on the upper-side, and if on the upper, the blotch does not take its 

 bearings from a rib. The leaf is invariably rolled transversely, not longitudinally, 

 the chamber being broadly triangular or cone-shaped. The larval head goes through 

 the same changes as in the alder insect, but it is of a darker tint, and always, I 

 believe, retains the frontal streaks after the last moult. The retention of the streaks 

 appears here to be a natural character, and not to be due to colour-intensification 

 from the effect of cold and retarded development, as it certainly is in the case of 

 the alder larvte found at the end of September and beginning of October. The 

 cocoon does not differ in its form and situation from that of the alder insect, but 

 the back of the pupa is smoky-black, and never, I think, shows the pale brown form 

 the other does. 



On two occasions finding an alder larva in its penultimate skin looking for a 

 leaf for its final chamber, I have given it birch instead, but on neither occasion 

 could it be prevailed on to use it ; and after two days the attempt was given up 

 and its natural food restored, when it set about its chamber at once. Here are 

 grounds, sufficient it would seem, for the establishment of a new species, but, when 

 we come to the perfect insects, the evidence is less satisfactory. It is true that tJic 

 alder insect is usually without any red tint ; that its costa is seldom yellow ; and 

 that a rather bright yellow costal triangle is never present, at least in any specimen 

 I have bred — characters, one or other of which is almost always present in the birch 

 insect. Yet, if a number are compared together, there will always be a few indi- 

 viduals that seem out of place in their own series, and as if they ought to be 

 transferred to the other. Under these circumstances, it will be wiser, perhaps, not 

 to multiply names, but to be content for the present with simply pointing out the 

 possibility of our having two species confounded together under G. elongella* 



It may, perhaps, be as well to add, that it is quite easy to distinguish between 

 the rolled leaves of thsee Oracilaria and those of the Tortrix, PhlcBodes immundana. 

 The chambers of the QracilaricB are more or less cone-shaped, that is, broader at 

 one end than the other, whilst those of the Tortrix, whether on birch or alder, are 

 cylindrical, and tightly rolled into a very small compass. The former insects merely 

 browse the inner surface ; the latter eats the wliole thickness of the inner rolls, 

 and only browses if food runs short, and it has to attack the outside roll. 



G.falconipennella. — Little, I believe, was previously known about this larva. 

 It lives upon alder, and is of extremely rare occurrence in my own district, but is to 

 be found in small but constant numbers in a dingle on the western side of the 



* Mr. Stainton has seen all my bred G. elongella (nearly forty specimens, pretty evenly divided 

 between the two forms), and I cannot do better than give his opinion in his own words. He 

 says: — "Ihe GracUarke, from the food-plant and different larval habits, ought to be distinct, 

 but I do not see where any character is to be found in the perfect insects, except in the gi-eater 

 redness of the birch species. In most of the alder specimens the total absence of any red tinge 

 is rather striking. 



" The species may be as distinct as pai and tridens, but yet quite as uudistiuguishable in the 

 perfect state." 



