36 
has it of the same colour as the rest of the wing. Some dark 
specimens of psi have a series of pale patches clown the hind margin. 
This is well seen in some of Mr. Raynor’s Brentwood specimens, and 
in the dark $ of cuspis. Something of the same sort may be detected 
in tridens, but it is never so pronounced. Still, all these matters 
of colour are, in fact, questions of degree rather than absolute 
differences. 
Mr. Burrows lent me some mounted wings of the two species, and 
examining these, I found that in the neighbourhood of the anal 
dagger the scales of tridens had the four (or other number) of 
serrations at the end of the scales quite level, i.e., of equal lengths. 
In psi the marginal were much shorter than the central ones. I 
thought I had discovered a further proof of the genius and insight of 
our beloved pastor, but alas, on pushing the research a little further, 
I found that these were individual and not specific variations. 
In Tutt’s British Noctiiae, i., p. 18, there are some remarks of 
mine on this question, to all of which I think I would still adhere, 
especially emphasising the fact that I had only certain races of the 
two species at my disposal. The more critical remarks by Mr. Tutt, 
that follow mine, are open to the same observation, and whilst they 
are equally valid now as they were when they were written, they 
must be read with the proviso I have several times called your 
attention to, that, whilst generally applicable, there are a good pro¬ 
portion of specimens of both species that present not the markings 
here predicated of them, but those of the other species. 
I think I have referred to all the points in which I can report 
differences between the two species, and one or more of them will 
suffice, in most instances, to enable which species some examples 
belong to to be determined. 
At Hereford I learnt to discriminate between them easily. When 
1 picked up a moth, I always knew which one I had got. But then 
it will be observed that the Hereford form of psi is only the pale one, 
and Hereford tridens was usually well coloured. Unfortunately, for 
purposes of illustration this evening, most of my tridens have been 
given away, many of my friends desiring authentic specimens, and 
especially those parted with included nearly all the most richly 
coloured ones. 
The discrimination would certainly be less facile between the dark 
London form of psi and the splendid large dark tridens, bred by 
Mr. Burrows ; but I think I could usually distinguish between them. 
In one of the boxes are the duplicates of these species from 
Dr. Mason’s collection; amongst these I picked out several that 
appeared Avrongly placed, and an examination of the appendages in 
the $ specimens verified my surmise in each case. 
Amongst the specimens exhibited are the series of tridens from Mrs. 
Bazett’s collection. They are all, eight in number, dark specimens of 
psi ; there is only one $ , and this opinion was verified by examination 
of this specimen. It is obvious that to discriminate the species must 
be difficult, when the “ tridens ” to be differentiated are, in fact, psi. 
I exhibit also the series of the two species from the Barrett 
collection. They include eighteen specimens of tridens of my own 
breeding, and one specimen of the bidens var. of psi. I found of these, 
and verified by examination of the appendages, that two specimens of 
