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.]
While spending the winter of 1875-76 in Apalachicola, Florida, I found
one of these _archippus_ swarms in a pine grove not far from the town.
The trees were literally festooned with butterflies within an area of
about an acre, and they were clustered so thickly that the trees seemed
to be covered with dead leaves; fig. 6 will enable the reader to form
some idea of their appearance thus grouped. Upon shaking some of the
trees a cloud of butterflies flew off, and the flapping of their wings
was distinctly audible. They hung in rows (often double) on the lower
dead branches, and in bunches on the needles. I find by my note book that
visiting the flock towards evening, it was receiving additions every
moment. I caught a net full off a bunch of dead needles, and, walking
away to some distance and letting them go, all but three returned to the
flock. The question as to where they came from seems a very interesting
one. I was told by Dr. A. W. Chapman that there was hardly Milkweed
enough in all Florida to produce one of these flocks, which doubtless
do not confine themselves to Apalachicola. During my visit I found two
more flocks not far from the first, but neither of these was as large. I
should mention that I often observed examples among them _in coitu_.
I have seen _archippus_ flocking at the Isles of Shoals, N. H., towards
evening, in very much the same manner, having flown nine miles from the
mainland. I have also seen clusters of _Vanessa J-album_ on tree trunks
at dusk in New Hampshire, which seemed to present a parallel to the
_archippus_ flocks, though of course on a very small scale.
R. THAXTER, Newtonville, Mass.