ALLOW me to point out that the lepidopterous insects said by Olafsen (not Olaffson) and N. (not R.) Mohr, to be found in Iceland, are not butterflies at all, but moths, as shown by the generic term Phalaena applied by each of those authors to every one of them—a term whose meaning your correspondent and his informant have failed to see. Those venerable authors, though dead and buried long before I ever heard of them, are old friends of mine, and I feel it incumbent on me to ask your readers not to impute to them this and other mistakes in Dr. Rae's letter. Whether there have been or still be butterflies in Iceland I am not competent to declare. I did not see any when I was there, but they may have got out of my way. I have, however, yet to learn that they exist in that country, and therefore I am inclined to believe Mr. McLachlan is right when he said that there are none. We have the testimony of the late Sir William Hooker (“Tour,” &c., ed. 2, vol. i. p. 333) that no butterfly had ever been met with in Iceland up to 1809, the year in which he visited that island. Gliemann (“Geogr. Beschreib. Isl.,” p. 165) in 1824 was unable to add to Mohr's list of twelve species of moths, and included no butterflies. If any of the latter have since been found it would be well for Dr. Rae to give his authority for the fact, otherwise his ingenious supposition that Icelandic butterflies and their larvae have been destroyed since 1786, is unnecessary, and his “only possible way” of reconciling “perfectly opposite authorities” falls to the ground through the absence of any opposition on the part of the authorities he has cited.