The Scottish Naturalist. T13 



expressed his belief that there was probably a third distinct 

 species. 



Let us now see on what grounds the three supposed, species 

 were separated. In Stainton's " Manual," where the descriptions, 

 though short, are generally very much to the point, the three 

 are thus described : — 



O. DiLUTATA. I "4"'- 1 "7"'. F.-w. pale grey or whitish grey, 

 with numerous transverse, wavy, darker lines and bands ; 

 frequendy a central pale band between two dark bands, the 

 outer of which is followed by another pale band; central spot 

 indistinct blackish. September (end), October. 



O. AUTUMNARiA. i"4"'-i"5'''. F.-W. morc glossy than in 

 Dilutaria, the second line more angulated near the costa ; f.-w. 

 a trifle more pointed than in Dilutaria, and rather smaller. 

 August. 



O. FiLiGRAMMARiA. i" i"'-i" 2,"' . F.-w. narrower and more 

 pointed than in Dilutaria (especially in the female), pale grey, 

 with numerous transverse, wavy lines, forming a darker central 

 band (or at least the edges of one) ; central spot black ; h.-w 

 whitish, with pale grey hind-margin. August (end), September. 



Moreover he adds that fiUgrammaria is much smaller and 

 autumnaria much more glossy than dilutata, though all three 

 are " very closely allied." 



In Newman's " British Moths," fiUgram?7iaria is said con- 

 stantly to differ from dilutata " in being of less size, and in 

 having the fore wings narrower and considerably more pointed." 



Not having at present access to Guenee's " Phalenites," I 

 cannot refer to his descriptions. 



My own investigation I began by trying if I could find any 

 structural differences by which the specific distinctness, or 

 the reverse, of the supposed three species could be proved ; 

 and in the male genital armature I have found such differ- 

 ences. 



On the ventral hind-margin of the last abdominal segment of 

 a male Oporabia are two short spine-like processes. In dilutata 

 (PI. I. A Fig. 2 and 3) these are rather near each other and 

 form short spines, longitudinally striate near the tip. In 

 autumnaria (B Fig. 2 and 3) they are rather farther apart and less 

 distinctly spine-like, while m. fiUgrammaria {fl Fig. 2 and 3) they 

 are much flatter and little more than tooth-like projections of 

 the hind-margin. Again, the lower margin of the harpagones in 



