90 



these two genera, Cilix and Drcpana, in neuration ; there are 

 many conspicuous differences. Vein 8 of the hind-wing in 

 Cilix anastomoses, or is coincident with 7 for the greater 

 part of its length ; only at the base and on the costal margin 

 is it separate. In Drepana vein 8 is distinct throughout, 

 aJthough it approaches 7 near the middle. Again, vein 6 of 

 hind-wing in Cilix commences close to 7, but is separate. 

 In Drepana vein 6 is out of 7. The cell of Cilix is also 

 considerably longer than in Drcpana. It might be wondered 

 if it were possible to have neurational characters that held 

 good among all the species of the group. There are, how- 

 ever, some constant characters. The hind-wing has no 

 pre-costal spur to vein 8, and vein i a is either absent or n(jt 

 reaching the tornus,* and if a supposed species oi Drepanidce 

 has not these two characters it would be ver}^ doubtful, 

 indeed, if it would ever be proved to be so, even with a full 

 knowledge of its life-history. 



The Noctitidce have rather a remarkably constant neura- 

 tion in spite of the variability of many of their numbers as 

 regards habit. They have been separated into two large 

 divisions — those that have vein 5 of hind-wing arising 

 separate from 4, and those that have vein 5 arising with 

 4, or near the corner of the cell. These two large 

 divisions have been known by the names of Trifince and 

 Quadvifincc. These names, however, are most misleading, as 

 meaning those species that have a median with three 

 branches and those with four branches, for many quadritid 

 species are not really four-branched. The division is 

 probably sound if we retain all those species that have vein 

 5 arising from nearer 4 than from the middle of the disco- 

 cellular vein as one division. We find that all the day- 

 flying species, such as Euclidia nil and E. glypJiica, Baiikia 

 angentula, Erastria fasciana, Toxocampa pastinuin (which is 

 only a partial day-flyer), Anarta niyrtilli, etc., have the vein 

 5 of the hind-wing arising nearer 4 than from the centre of 

 the cross vein, going to show that here, also, the altered 

 habit of day-flying with the attendant alterations in the 

 actual flight is largely correlated with an altered neuration. 

 Those species of Noctnidce that fold their wings very closely 

 together usually belong to the trifid section with vein 5 

 from the centre of the cross vein. In a very large number of 

 species this vein is so reduced as to be present onl3^as a fold 

 of the membrane, without having the true function of a vein. 

 Although vein 5 of the hind-wing varies so considerably in 



* Vide Hampson, " Cat. Phalasna?,'' i, p. i8. 



