LITHOSID.^. 



205 



There is variation in the intensity of the black dots form- 

 ing the two transverse lines, especially in the middle area of 

 the fore wings, where, in rare instances, the black colour also 

 runs along the nervures between them, thus forming a black 

 V, or even by a similar union of the outer dots the figures 

 IVI in a prostrate direction. These forms, though rare, 

 have been repeatedly obtained, and in the collection of the 

 late Mr. F. Bond is one so marked on one side only ; while 

 Mr. S. J. Capper has one with the markings thus VI, the 

 upper pair of dots not united. Another striking variety in 

 Mr, Bond's collection has a broad smoky band along the hind 

 margins of all the wings, and three black streaks from the 

 base of the fore wings ; another belonging to Mr. C. A. Briggs 

 has the fore wings regularly suffused with smoky grey-brown 

 and the hind wings yellow-brown. In mountain districts in 

 France and Switzerland, especially at high elevations, varia- 

 tion is further extended and more pronounced ; a form with 

 all the nervures of the fore wings smoky-black throughout, 

 and with cloudy hind wings, is known as variety Andereggii, 

 while another, even more broadly black veined, with blackish 

 hind wings, is called Biffaknsis. The variety with the central 

 black V is known as signata, but these varietal names are 

 of little moment, the varieties being themselves unstable and 

 varying towards each other. (It is somewhat remarkable 

 that in several allied species (?) precisely similar aberrations 

 occur — >S^. roscida, in which both sexes are of the form and 

 size of the female irrorclla, with similar spots, but of a deeper 

 general ochreous colour, having a variety, called melanomos, 

 in which the hind wings are clouded with smoky and the 

 fore wings smoky-black from the base ; S. aurita, which is of 

 a rich ochreous, almost orange, with much larger subterminal 

 spots, but otherwise similar to irrorclla, having a form known 

 as Eamosa, with black stripes down the nervures of the fore 

 wings ; while ,S. KuJihveini, which is also of a deep ochreous 

 yellow, has the additional spots on the hind wrings near the 

 margin as in strongly marked irrorella. These species are 

 not known with us.) 



