264 THE ENTOMOLOGIST. 



THE ATHALIA GEOUP OF THE GENUS MELITMA. 

 By Eev. George Wheeler, M.A., F.E.S. 



(Continued from p. 243.) 



The small cross nervules representing the secondary bifurca- 

 tions of iii, and the junction of iij with iii^, and iiig with iv.^, 

 and which form the outer edge of the discoidal cell, are amongst 

 the most characteristic parts of the neuration of the fore wing 

 both in shape and texture. They are very thick and strong in 

 varia and dictynnoides, and almost as thick in asteria and 

 aurelia ; fairly thick in athalia generally, but rather variable in 

 this species, thicker in herisalensis than in typical deione, in 

 Swiss than in Italian partJienie, and in dictynna than in hrito- 

 martis, though they are by no means thick in any of these ; 

 they are, indeed, very thin in southern parthenie and in deione, 

 and in britomartis are so slight that they tend to melt away with 

 the action of the chemicals used in denuding the wings of their 

 scales — at any rate, in the case of those portions which belong 

 exclusively to iii, which are always somewhat slighter than the 

 rest, the thinnest part invariably being the upper fork of the 

 lower branch of the obsolete iii. The junction of iii^ with iir,, 

 when it exists, and that of iiig with iv^, always points from the 

 base upwards, generally sharply, though the former nervule 

 in the case of britomartis makes a wide angle, sometimes quite a 

 right angle. The other four nervules, which belong to iii, may 

 be said normally to form a somewhat straggling W, a formation 

 which is very clear in M. merope, and it is by the flattening of 

 some of these lines and the extension of others that the charac- 

 teristic differences in the shape of the discoidal cell are pro- 

 duced. I shall call these nervules " the W," and speak of them 

 as the first, second, &c., strokes of the W, counting from the 

 costa downwards. The outer edge of the discoidal cell is flattest 

 in varia, and most irregular in parthenie, but, though this is 

 always true of the former, yet the degree of flatness or evenness 

 varies. The first three strokes of the W are generally flattened 

 out into an almost straight line, though ihe first two sometimes 

 form the base of a U, and the fourth stroke makes with them 

 an angle of only about ITO"^. The same formation obtains in 

 asteria, except that a much sharper angle is formed by the 

 fourth stroke, giving the effect of a slight peak at the lower outer 

 corner of the discoidal cell. This peak is very distinct in 

 aurelia, the first three lines being sometimes nearly straight, but 

 the W sometimes very distinct, even in insects taken at the same 

 time and place ; the peak is sharper and even more distinct in 

 dictynnoides, and the W sometimes plainer, the third stroke 

 standing distinctly away from the first two, even if the former 

 are rather a shallow U than a V. In athalia this peak is very 



