40 
review a few of these summarised papers, and then goes on to criticise 
at length one view that I brought forward, viz., the connection between 
moisture and melanism. In my pamphlet I proved conclusively that 
areas, which were excessively humid, and those that had by recent arti¬ 
ficial change of environment, produced dark surfaces, &c. (such being 
frequently increased by rain), also produced melanic races of certain 
species, and these, I considered, essentially due to three things, (1) the 
action of the moisture constitutionally on the larva ; (2) the darkening 
of the surfaces by rain, smoke (or both combined), etc.; (3) the general 
action of “ natural selection.” 
To begin with, the title of Mr. Robson’s j3aper is essentially mis¬ 
leading as a criticism. If he had written “ Is moisture a cause of me¬ 
lanism ? ” we might have obtained some useful result, but “ the cause ” 
obviously shuts out all other considerations, and at once levels the 
paper to a reductio ad absurdum. 
I will now consider a few of the points touched upon. Mr. Robson 
begins by the effusive praise of a paper of Mr. Birchall which was 
written in 1876, and which made some comprehensive generalisations 
without working out or even suggesting any reason which could be 
acted on by scientific men. Dr. White seems to have been the only 
man who got near a comprehension of the subject at that time. To say 
that Mr. Birchall’s paper “ comprises almost everything that has since 
been written on the subject,” is an opinion ridiculous in itself, and can 
only be meant to throw dust in the eyes of those entomologists who are 
not scientific, and is disproved by Mr. Robson’s own paj^er, since he 
finds something else to write about. Such a statement of such a paper 
is not likely nowadays to pass muster with men who read and think 
for themselves, and who begin now where the entomologists of twenty 
or thirty years ago left off. Even Mr. Robson says of Mr. Birchall’s 
paper, in his next paragraph, that “ many points briefly touched on by 
Mr. Birchall were afterwards discussed at length.” 
Mr. Robson refers in a very strange manner to certain remarks made 
by Mr. Dobree (D’Obree of Mr. R.’s paper), in which he showed that the 
NocTUiE of high latitudes were not necessarily melanic. He says that 
Mr. Dobree “ is a student of Nocture only, and that no conclusion based 
on the study of an entire Order could be upset by one portion of such 
Order.” But where, I would ask Mr. Robson, can melanism be so well 
studied as among the Noctu^: ? For every example of melanism in the 
other groups of Lepidoptera, Nocture give a dozen. In fact, it is only 
among this family that sufficient material can be gathered for generali¬ 
sation, the examples among the Geometry being much more limited (as 
might be expected from their general habits and the action of “ natural 
selection ”), and, with very few exceptions, limited to those species 
whose habit it is to rest on tree trunks, fences and similar places. 
Mr. Robson’s reference to Lord Walsingham’s i:>aper, which has 
been discussed at length previously, is unfair to its author, since Lord 
Walsingham had already withdrawn his statement “ that melanic forms 
were characteristic of high latitudes,” and has substituted “ suffused 
forms ” (Trans. Ent. Soc. Lond., 1890, pp. liv.-lv.), and it appears to be 
begging the question, so far as Mr. Robson is concerned, to repeat the 
statement. Lord Walsingham’s paper simply shows that dark coloration 
may be an advantage to the insects possessing it in high latitudes and 
altitudes, but it does not attempt to show the cause of melanism, which 
is what we have to deal with. 
