MBILANISM AND MELANOCHROISM. 
31 
very readily accept an already prepared tubular hollow, or will 
perform all the work of excavating one for itself in rotten wood 
or in the pith of a piece of elder twig, and in this case closes the 
opening with the top of the cocoon. In default of a more suit- 
able nidus it will go down into sawdust or even earth, forming 
an ordinary cocoon of silk and the surrounding material. 
I have already referred to the fact that on one occasion half 
of a certain brood emerged in August as an autumnal brood, 
in time enough for a second brood to have occurred, but that 
on no other occasion among hundreds of moths has an 
autumnal specimen shown itself. This shows that it is very 
unsafe in the matter of habits of this sort to regard as invari- 
able in a species, any habit, which we may have found to be so, 
in even a very large experience. 
This consideration prevents my saying that tridens never 
has four-moult larvae, so frequent in some species, but I have 
never detected one. 
Tridens occurs here at precisely the same seasons, and in 
precisely the same places as psi. Wherein they differ in habit, 
why there is room for the two species, why the one does not 
displace the other, are matters on which I have still everything 
to learn. Tridens like psi, will eat almost anything arboreal, 
but I think it has a closer relation to rosaceous plants than 
psi, especially fruit trees, and is perhaps commonest here in 
pear orchards ; whilst psi is at least equally at home on forest 
trees, and may be met with on oak, birch, etc., on which I 
never happen to have taken tridens. I have a suspicion that 
the fine pink tinge that has characterised some of my broods, 
and which occurs in several Acronyctas as a variety, is here 
related to cherry as a food, but I have instituted no special 
experiments to test the point. 
{To be continued.) 
MELANISM AND MELANOCHROISM IN BRITISH • 
LEPIDOPTERA. 
By J. W. TUTT, F.E.S. 
{Continued from page 7.) 
Although not directly bearing on British lepidoptera, I 
referred {Entomologist's Record, etc., vol. i., pp. 122-125) 
to an article by Mr. W. W. Smith, of Ashburton, New Zealand, 
“On the Variation of Argyrophinga antipodum," to show that 
my theory of excessive moisture producing melanism, and vice 
