2 Is Vanessa Polychloros
tone than is usual, sufficiently so to attract special notice.
The imago is rather below the average measure of Poly-
chloros in expanse of wings, being about the usual size of
Urtica (two inches). The insect is the only individual of the
brood known to have varied, even in the slightest degree.
Although I did not see every member of the brood, I can
vouch for at least forty or fifty specimens, which I examined
carefully, and found not a trace of variation in any single
case. No larvae of any other species of Vanessidae were reared
contemporaneously with the brood.
I have examined the antennas of this specimen under the
microscope, and find that they present the special characters
found in Polychloros.
From these facts I make four deductions, all of which turn
upon points of interest. It is from such instances of diver-
gence as the present that we are enabled to gain some clue
respecting the affinity of species known to be closely related,
and for this reason I offer the following observations :—
1. As Polychloros lives upon elm and other trees, and
Urticae upon nettle and low plants, the instance is valuable as
affording further evidence of the fact that neither a par-
ticular food nor a change in diet affects in any way the
colouring and markings of the perfect insect, so as to offer
per se a means of originating "varieties." This conclusion
is valid whether the specimen under consideration be really a
Polychloros or Urticae. Many experiments upon different
species of insects agree, I believe without exception, in so
deciding this question.
2. On the supposition that the specimen is the product of
Polychloros parents, it is easy to infer either that the ovum
was dropped whilst the female was on the wing, or else that
the young caterpillar fell from a neighbouring tree soon after
emergence from the egg ; in either case the accident must
have occurred immediately over the Urticae web. As the
broods of the two species rarely appear synchronously, the
conjecture is scarcely to be entertained, even if the accident
were probable. On such a supposition, however, it is to be
deduced that (if Polychloros) the society of an allied species