18 VARIETIES OF NOCTTLS! 



portant character is the elongation of the anal angle into a sort of 

 hook, the inner margin being rounded towards this point so as to give 

 it this particular character and appearance. Guenee writes : " The 

 perfect insects are, without exception, extremely beautiful. Some are 

 noticeable only for their satiny, bronzy, or reddish-brown decorations, 

 of which the most noticeable precedes the outer margin and reaches, 

 on becoming narrower, the median space behind the extra-basal 

 (complete basal) line; but the greater part of the species, besides 

 these decorations, which are found to exist in almost all of them, carry 

 a particular or special ornament. This consists of one or two spots 

 placed under the cellule, quite peculiar to this genus, and agreeing 

 with neither of the three ordinary stigmata. These spots which I 

 shall name in my descriptions " signes subcellulaires " are coloured 

 with a substance resembling polished gold or silver in colour and bril- 

 liancy. They are slightly raised on their edges, as if some drops of these 

 rich colours had fallen on the wing and had sunk in the middle in 

 drying. But they are not the less composed, like the remainder of 

 the wing, of imbricated scales, of which the exterior ones form a 

 kind of pleat or raised margin with a rounded contour, instead of 

 being arranged transversely, as are the other scales of the wing, even 

 those which form metallic spots, often as brilliant as these particular 

 signs. But it is not only for their brilliancy that these signs are 

 remarkable, but also for their form which is not less essential, and 

 which enables us readily to distinguish the species. Sometimes they 

 are simple rounded decorations, sometimes they are two contiguous 

 points, generally the posterior sign only has the form of an oval dot, 

 whilst the anterior is shaped more or less like a rounded hook re- 

 sembling a Y or U or a note of interrogation, deprived always of its 

 dot below ; lastly, the two marks sometimes join, and then the 

 posterior takes the form of a drop and the whole resembles roughly a 

 a gamma or lambda reversed, of which the buckle would always be 

 blocked (filled in). All these names of letters have been used to de- 

 signate the species of Plusia, although the resemblance to these alpha- 

 betical symbols is not always very striking. There is yet a 

 character that should not be omitted when speaking of the genus 

 Plusia. It is a tooth formed at the anal angle of the fore wings which 

 varies in size according to the species. I call it the "anal tooth." 

 Some Plusice have scarcely a trace of it, as the species egenda and 

 illustrata ; in others it is very much developed, and the inner margin 

 takes the form of a deep sinus, so as to meet this prolongation at the 

 anal angle. This is seen in P. signata, cerea etc., but that in which it 

 is most pronounced is the curious species which I have named 

 thyatyroides. Lastly, another character which is presented in a certain 

 number of the species of Plusia is two tufts or plumes of scales 

 which are found on the sides of the abdomen, and which are pressed 

 against the segments following, sometimes following the sides, some- 

 times almost joining at their extremities over the back. I have not 

 referred to the plumes on the thorax, which are, however, very re- 

 markable in this beautiful genus, but all entomologists have noticed 

 these on the specimens in our collections " (' Noctuelles,' vol. vi., 

 pp. 325-326). This is a remarkably good account of the principal 

 characters of the imagines of this most interesting genus. 



