THE TREBLE-BAR. 149 



The moth Is out in June, sometimes late May ; it is exceed- 

 ingly local in Britain, and only occurs in the Breck district, 

 where it was first met with about fifty years ago. Tuddenham, 

 in Suffolk, is a noted locality, as also is Thetford, in Norfolk. 



r^^*^^ Thi. 



The Treble-bar {Aiiaitis plagiata). 



M 



\u This is a greyish white species, of which specimens of both 



l-^ generations are shown on Plate 55, Figs. 6$, 7 $ (ist 



^r* generation), Fig. 8 J (2nd generation). The chief variation 



v^ji, is in the cross central bars of the fore wings, which are 



/.^ sometimes much widened, and occasionally joined from the 



middle to the inner margin ; or the space between these two 



bars is more or less filled up with dark grey. On the other 



hand, the bars are sometimes very faint, but such aberrations 



are perhaps most frequent in the second generation, which 



consists of smaller specimens. 



The long caterpillar is brown, inclining to reddish or to 

 greenish, with several darker and paler lines on the back 

 and a yellowish line low down along the sides. It feeds on 

 St. John's wort (^Hypericiwi) in June and July ; the caterpillars, 

 hatching in the autumn, are not mature until the following 

 April. 



Usually there are two generations of the moth, the first 

 appearing in May and June, and the second in August and 

 September. The species is pretty generally distributed over 

 the British Isles, extending to the Hebrides and the Orkneys ; 

 and will probably be found in all localities where its food plant 

 occurs freely. It affects cliffs and sandhills by the sea, rough 

 places on chalk slopes, and sometimes the moths fly up in 

 numbers as we walk over the herbage in such spots. 

 The range abroad extends to Western India and Japan. 



