20 
themselves to Mr. Pierce for inspection, and he also was able to separate 
them from their scale markings, etc. ; he thinks he was guided chiefly 
by the attenuation of the central fascia of unidentaria on the inner 
margin (mentioned by both Haworth and Stephens in their diagnoses, 
though unfortunately not very constant). I am indebted to the kindness 
of Messrs. Battley, Nicholson and Jackson in lending microscopes for this 
evening, and I trust you will all avail yourselves 
of the opportunity of verifying Mr. Pierce’s 
observations on the genitalia. It may be of 
interest to mention that Aurivillius in his new 
work on the Scandinavian lepidoptera ( Nordens 
Fj arilar, 1891) also differentiates ferrugata and 
unidentaria in this way. 
c. unidentaria. c. ferrugaria. M y attention lias also been called to one 
other structural difference, and that is in the 
matter of scale structure, which has been so zealously and with such 
interesting results taken in hand by Dr. W. S. Biding. He has rendered 
me most willing assistance in examining specimens and tabulating the 
results as regards the proportion of scales with different numbers of 
teeth, and I am pleased to be able to hand round, for the inspection of 
those who may desire to look into them, his very carefully prepared 
tables. He suggested that I should also ask other friends to work inde¬ 
pendently of him with a view to verifying his results; and I found in 
my kind friends, Messrs. A. U. Battley and A. Bacot, very ready 
assistants. 
M ithout going very fully into details, the general result of investi¬ 
gations along these lines, by Dr. Biding and Messrs. A. U. Battley and 
A. Bacot, seems to be that however much the scale structure of indi¬ 
viduals of a species may vary inter se, yet ferrugaria, Haw. has always 
a considerably larger number of many-teethecl scales than unidentaria. 
Of 10 ferrugaria examined, two showed no 3-toothed scales, while 
of 11 unidentaria three or four showed no 6-toothed, two none even 
5-toothed, and none any with more than six teeth, while several ferru¬ 
garia had some 7-toothed scales, and one an odd 8-toothed. To sum up, 
ferrugaria gave 43 per cent, of scales with 2, 3 or 4 teeth, and 57 per 
cent, with 5, 6 or 7; while in unidentaria 82’6 per cent, had but 2, 3 or 
4 teeth, only 17-4 per cent, having 5 or 6, the percentage of 6-toothed, 
indeed, being but -2. 
Mr. Bacot also called my attention to a large number of toothless 
scales in one or two specimens, these appearing to be non-pigmental. 
Mr. Battley further remarks (in litt., Feb. 26th, 1894), that “ there 
is also a decided difference in shape ; ferrugata has the teeth pointed 
and generally distinct, the centre teeth being almost invariably longest, 
and projecting beyond the others; unidentaria has the notches between 
the teeth rounded, the teeth less distinct, and the centre teeth generally 
further back than the outside ones. The scales of ferrugata look much 
more jagged than those of unidentaria .” I shall hope to pursue this 
subject further at some future time, as I have already some very in¬ 
teresting notes and observations from the gentlemen whom I have 
mentioned. But I introduced the subject here in order to throw a little 
additional light on the specific distinctness of the two insects, and need 
only add that a purple variety of unidentaria examined by Dr. Biding 
agreed with the black forms. 
