74 THE CANADIAN kNTOMOLOGIST. 



All these colours may cccur with or without the dark bands, oi there 

 may be combinations. The first five colours Fetm to be most comm.only 

 met with, the white-banded form being the rarest. Now, according to my 

 theory, we should find all the above vaiiations of colour with \)a\\n of 

 approximattly the same length, which we do find ; and this enabled me 

 first to see my way clear through the variations. Food-plants, I feel sure, 

 play an important part in the colour variation, as does altitude; mountain- 

 ous forms varying more than lowland. I should like to make the revision 

 more complete by compaiing the life-histories of the American specits 

 with those of the European, and also the genitalia, but unf I this can be 

 done my work will remain rather crude, but, at any rate, a ready means of 

 grouping them. The specimens examined were mostly loaned, so that is 

 why 1 have done so little work on the genitalia, and it may be possible 

 ihit the Uue /urcafa Thunb. is not found in North America, the variety 

 qii'uiquefdsciata Pack, taking its place here. This point can be, perhaps, 

 decided on a more complete comparison with the European form. The 

 length of the palpi seems to be a very constant character, and I examined 

 some six hundred specimens. It is surprising that the older authors like 

 Packard and Guenee failed to notice this, Packard having lumped species 

 vviih very long palpi, such as glaiicata Pack., bistriolata Zcll., with such 

 species as fiiibilofasciata Pack, and furcata Thunb., in which they are 

 short, Hydriometia furcata or its variations have never been taken in 

 New England, and I should say are strictly western. Just what the 

 boundaries are I cannot say, as the species have been so confused. I 

 notice one difference between European and American forms oi furcata, 

 that is the basal band is heavier and wider in the latter than in the Euro- 

 pean form, but I would hesitate to separate them on such slight differences. 

 Both forms have sometimes a white streak on inner margin of fore wings, 

 but this is not always present. 



Taking the species of Dyar's List, and applying my palpi and 

 colour scheme they would arrange as follows : 



I. Hyclriomena furcata Thunberg, Diss, Ins. Suec , pt. i, 1784. 



— sordidata (of author?) not Fab. 

 Short palpi, cinereous ground colour. 



The true furcata (like fig. 10, table 3) may not occur in North 

 America, as I have not seen a specimen exactly like the European form, 

 and the forms seem closer to quinquefasciata Pack. \\\'a.x\ furcata. IT it is 

 found here, tire west will jtrobably be its home, as none of the varieties 



