18 VARIETIES OF NOCTUJG 



in the females. It is well known, however, that the markings of both 

 are so similar that very few lepidopterists can separate them with any 

 degree of satisfaction. The principal markings are a trident-shaped H$ 

 longitudinal black mark at the base of the wing, the ordinary stigmata, 

 a very distinctly elbowed line beyond the reniform, and a short 

 oblique, dark shade running from the costa to the stigmata. It is, 

 therefore necessary for readers to bear these general facts in mind to 

 understand the points of distinction mentioned. Dr. Chapman writing 

 to me says : " You will see that tridens is a very variable insect 

 within limits, whilst psi is very uniform (bidens, apart). The general 

 facies at once distinguishes tridens and psi ; let anyone mix one of 

 either set with the other, and you can pick it out at once. This is 

 probably because I have only one type of psi. When you look for 

 any marking apart from tint and tone, to separate psi from tridens, I 

 must confess that I have been able to find none that is invariable, the 

 shortness of the dagger handle at the anal angle, whiteness of hind 

 wings of male, do not hold universally. Another mark, that is perhaps 

 better than either of these, is the double mark in the fringe at the anal 

 angle at the end of the dagger ; exaggerating a little, it consists of two 

 lines in psi, two blotches in tridens ; but this fails sometimes, and is 

 not distinct enough to depend on description, apart from comparison. 

 It is curious how similar varieties affect these species ; in both, the 

 stigmata are usually united, but in both sometimes separate. Then 

 the blotch on the costa above the stigmata is sometimes a line, some- 

 times a blotch, sometimes descends into the orbicular, sometimes into 

 the reniform stigma, sometimes falls short between them, but equally 

 so in both species." This is a most valuable summary and, backed up 

 as it was with Dr. Chapman's insects, I am able to add under each 

 species my own notes, which are really an extended form of those of 

 Dr. Chapman. I would however call attention to one or two minor 

 points. The dark shade from the costa between the stigmata is some- 

 what different in tridens and psi in my opinion. In tridens it does not 

 appear usually, to go between the stigmata, but generally strikes the 

 upper and inner edge of the reniform, while in psi it crosses, more 

 generally, obliquely between the reniform and orbicular. Again, the 

 transverse line parallel to the hind margin is distinctly double in 

 tridens, but the inner edge is, to a great extent, lost in psi : in tridens, 

 too, this line commences rather farther over than in psi, but the most 

 remarkable point about this line is that in psi, the lower portion is gene- 

 rally nearly vertical or slightly turned back towards the anal angle, 

 while in tridens it goes distinctly towards the centre of the wing, ending 

 under the orbicular or quite at one third from the anal angle ; this is 

 fairly constant ; occasionally one finds in a specimen of tridens, as it 

 extends in this direction, a slight backward curve before it reaches the 

 inner margin, but it is very characteristic in Dr. Chapman's magnifi- 

 cent series. The anterior wings are less distinctly marked in psi with 

 black markings than in tridens. In both species there is a distinct line 

 of demarcation passing straight through the anterior fringes from apex 

 to anal angle. In tridens, the inner half is ochreous, the outer whitish ; 

 in psi, the inner half is darker grey than the outer and not ochreous ; 

 in the rosy specimens, the fringes are shaded with the same colour. 



