IN THE BRITISH ISLANDS. 143 



very striking ; mine, however, is a slight modification of Treitschke's, 

 having the abbreviated basal line, which is generally absent, marked 

 in the same striking manner. 



Hydrilla, Bdv., palustris, Hb. 



This species, which is excessively rare in Britain, and far from 

 uncommon upon the Continent of Europe, presents very marked sexual 

 variation. Regarding this Guenee writes : " The genus Hydritta, as 

 now understood, is one of the most abnormal in this or neighbouring 

 families. The most remarkable fact which is presented is the difference 

 in the sexes. One can say, without exaggeration, that it is in the 

 Noctuelles, analogous to Chemerina in the Geometrina, and to the genus 

 Diurncea in the Tineina, so much is the female disproportionate to the 

 male in shape and form. One might take the former for an abortive 

 specimen " ( Noctuelles,' vol. v., p. 237). The type of this species is 

 represented in Hiibner's fig. 367, which is " a male of a greyish-brown 

 ground colour, with one irregular transverse basal line, traces of the 

 reniform, and two transverse lines (roughly parallel to the hind 

 margin) outside the reniform." This figure is nearly twice the size 

 of the small female figured in Newman's * British Moths,' p. 311, which 

 has two dots instead of the first transverse line (before the stigmata). 

 The description in this work is a direct translation of that in Guenee's 

 'Noctuelles,' vol. v., pp. 237, 238. The Caradrina exilis of Eversmann's 

 1 Bull, de la Soc. de Mos.,' 1842, iii., p. 548, is the ? of this species and 

 the same author's diagnosis of exilis from the ' Fauna Lep. Vol.-Ural,' 

 p. 261, is as follows : " C. exilis. Alis anticis augustis subparallelis 

 obtusis, saepe obscuratis brunneo-fuscis unicoloribus posticis griseis." 



Acosmetia, Stphs., caliginosa, Hb. 



This species is not very variable in Britain, although the type, 

 represented by Hiibner's fig. 474, is somewhat different to our specimens. 

 The colour of the anterior wings is grey-brown, with a transverse basal 

 line, then the ordinary stigmata, then a transverse row of dots out- 

 side the reniform, and lastly a double transverse line parallel to the 

 hind margin ; there is also a dark shade from the base of the reniform 

 to the inner margin. The hind wings are darker on the margin than 

 at the base. Haworth's lutescens is simply a redder form of this species, 

 the same form that Guenee describes as caliginosa. There are sometimes 

 traces of the basal line being double, and, instead of the shade from the 

 reniform to the inner margin, there is usually an angulated line 

 directly outside the reniform ; the outer line, too, is very pale in our 

 specimens ; the reniform is also very pale, and there is rarely any 

 trace of the orbicular. Guenee describes another Acosmetia as aquatilis, 

 Bdv., but Staudinger treats this as a variety of caliginosa, simply adding 

 in his ' Catalog ' " dilutior." The female of this species is strikingly 

 smaller than the male. It is therefore only needful to notice the fol- 

 lowing forms : 



a. var. lutescens, Haw. Haworth thus describes this variety 

 which he treats as a distinct species : " Phytometra (the reddish Buff). 

 Alis subunicoloribus sordide ruf o-lutescentibus ad marginem crassiorem 

 rufis ; posticis subfuscis." " Cilia omnia rufescentia, anticarum satura- 

 tiora " (* Lepidoptera Britannica,' p. 260). This reddish form is gene- 



