OPORABIA CHRISTYI, PROUT : A DISTINCT SPECIES. 85 



Oporabia christyi, Prout : A distinct species. 



By J. E. E. ALLEN, M.A. 



Oporabia christyi is described by Mr. L. B. Prout {Ent. Rec, vol. xi., 

 p. 122) as an aberration of 0. dilutata, with the remark that it "seems 

 inclined to form a local race in some places." The description is as 

 follows : " Pale grey or dirty-white, glossy, weakly marked, central 

 spot of forewings extremely small, second line angulated almost as in 

 0. autumnata, Bkh., and 0. filvirammaria, H.-S." It is figured in 

 Entom., vol. xxxiii., pi. ii., figs. 7 and 8 (March, 1900), with some 

 further remarks, in the course of which Mr. Prout says " At one time 

 I fancied it might be a distinct species." I have had the opportunity 

 of studying this form at Enniskillen somewhat minutely for some 

 seasons past, and I am strongly of opinion that it ought to take rank 

 as a species. The evidence of its specific distinctness falls under three 

 heads : (1) Difference in markings in the imago. (2) Extreme local- 

 isation. (3) Fidelity to type. I shall be able to state the evidence 

 more fully at the end of this article, after presenting all the data which 

 I have been able to obtain as to its general characteristics, variation, 

 habitat, etc, 



Mr. Prout's description, quoted above, stands as the original 

 diagnosis of the species. I may here add that its most striking 

 featvires are — smaller size as compared with 0. dilutata : pale clear 

 ground colour, especially in the female, as compared with the corres- 

 ponding local form of 0. dilutata ; tendency of the transverse lines to 

 group themselves into bars, a bar of two lines within the central spot, 

 and a bar of three lines outside it ; tendency of the lines in the male 

 to become obliterated, except on the costa, inner margin, and nervures; 

 wide curve of the outer line round the central spot ; glossy and rather 

 fragile general appearance. In some respects it is intermediate between 

 0. dilutata and 0. autumnata : e.g. — ground colour, 0. dilutata, dingy 

 brown-grey, 0. christyi, clear grey or straw-colour, 0. autumnata, 

 silver-grey (this distinction is clearly seen in Irish specimens of 0. 

 christyi, but not in those from the south of England) ; outer line, 0. 

 dilutata, often curved inwards to touch central spot, 0. christyi, curved 

 or obtusely- angled outside central spot, 0. autumnata, bent at a right 

 angle outside central spot. Mr. Prout has pointed out to me another 

 characteristic of 0. christyi, viz., the arrangement of the dots on the 

 margin of the hindwings. In 0. dilutata they are uniform along the 

 whole margin ; in 0. christyi they are most conspicuous as three pairs 

 of dots towards the tornal end of the margin, the apical portion being 

 often almost plain. In this respect also 0. christyi resembles 0. 

 autumnata, but the character is not constant, as a few of the most 

 distinctly marked 0. christyi have the dots along the whole margin. 



Variation. — 0. christyi varies in ground colour, and intensity and 

 position of the transverse lines. The pale grey is, sometimes in the 

 male, generally in the female, tinged with straw-colour. At Epping 

 a form occurs in which the whole of the wing area has the appearance 

 of having been washed over with a brownish tinge, the transverse lines 

 being sometimes partially blurred. This form also occurs occasionally 

 at Enniskillen. It does not merely represent the extreme limit of 

 gradual divergence from the type in the direction of infuscation, for in 

 that case we should find it less common than the less extreme forms ; 

 April 15th, 1906. 



