Allied to _marculenta_. Of the same bright yellow, shading to ochreous at base of primaries on costa and sides of the thorax in front. Ornamentation sub-obsolete. This species wants the subterminal line of _marculenta_. Instead there is a vague and broad darker shade only visible with attention. The outer line is rounded outwardly over the median nervules, as in _trimaculalis_. It is apparently disconnected below vein 3, appearing again higher up below the open reniform and describing an inward curve above vein 1. The orbicular dot is imperceptible and the inner line very faint. Fringes faintly discolorous, being pale fuscous, concolorous with the lines. Hind wings very pale fuscous with a slight yellow cast. The line is continuous, squarely projected over median nervules, very different from allied forms. A pale terminal line before the pale fuscous fringes. Beneath largely washed with fuscous, legs outwardly white. On primaries the marking of the upper surface reappears relieved by pale interspaceal blotches; hind wings pale fuscous, uniform, with the line repeated. Palpi white beneath, dark at the sides. _Habitat_, Hamilton, Ontario, Mr. Moffat. The species seems a little stouter bodied than _marculenta_, of about the same expanse. CORRESPONDENCE. SWARMING OF ARCHIPPUS. DEAR SIR,— The assembling of _D. archippus_ referred to in CAN. ENT. is perhaps not so frequently noticed as their passing over localities in flocks. Several years ago I saw them congregating in a bit of woods in the neighborhood of the city which I was visiting at the time. At least every other day they were hanging in a listless kind of manner to the underside of branches in immense numbers, with their wings closed, and not noticeable unless disturbed, very few being on the wing. Their favorite resting place seemed to be dead pine twigs, which would be drooping with their weight, and in more than one instance I saw one too many light and the twig snap, and send a dozen or more into the air to seek for another perch. In going to and from the woods I have seen several of them at once coming from different directions, high in the air, sailing along in their own easy and graceful way, all converging to the one spot. I did not see them depart. I went one day and could not find one in the woods; and as there were thousands, perhaps hundreds of thousands of them, it would have been a fine sight to see them go. The following year they were remarkably scarce and it was three years before they were even moderately plenty. J. ALSTON MOFFAT, Hamilton, Ont. SWARMING OF ARCHIPPUS. DEAR SIR,— I was surprised to learn from the letter of Mr. Edwards in your last issue, that the flocking of _archippus_ is not a well known fact in Entomology, and in view of this I venture to add a few facts in regard to it which may be of interest. [Illustration: Fig. 6.]