851 



or completely disappear, fore- and hindwiiig or one of them becoming 

 selfcoloured. 



The comparison of the upper side of the forewings in different 

 specimens of Arctia caja already leads to the conviction, that the 

 capricious winding of the white interspaces between the dark-brown 

 areas may be deduced from a regular alternation of light and dark 

 transversal bars. For along the anterior margin this regularity is 

 unmistakably present in all specimens, as well as in the majorit}' 

 of the remaining Arctiïdae and in cognate families, seven dark 

 blotches alternating with six light spaces, if we count from the 

 wingtip to the root, the latter being frequently covered by a narrow 

 white tegulum. Indicating the dark spaces with the cyphers J to 7, 

 the light bars with the letters A to F, we observe that A, B, E 

 and F communicate with a longitudinal white streak, which winds 

 along the median part of the wingflat from the root till near the 

 outer margin, and sends out four transverse branches to the back- 

 margin. The question arises, whether these branches may be con- 

 sidered as the prolongations of a corresponding number out of the 

 5 anterior transverse bars, and if so, of which of them ; I prefer, 

 however, to leave this question unsolved for the present. The white 

 bars C and D on the contrary are isolated spots; D reaching to 

 the radial nerve, C advancing somewhat farther towards the middle, 

 and so entering ihe discoidal cell. 



The light bars are not all of the same width, but they generally 

 are somewhat narrower than the intervening dark spaces; yet in 

 different specimens the dimensions are highly variable. 



This variability has been studied and statistically arranged for 

 a very extensive material by K. Smoijan ^). As however his investi- 

 gations do not in the first place touch on the phylogeny of the 

 colour-pattern, they need not be considered here further. 1 only 

 wish to remark, that Smolian also assumed seven dark and six light 

 transverse bars on the forewings, and found them back on the hindwings. 

 Of this set of six lightcoloured bars on the forewings a certain 

 number, varying from nought to six, might reach the hindmargin. 

 A look however at the fourteen schematic figures, by which Smolian 

 represents these seven cases with their various sub-forms, shows 

 that in none of them except the very- last one (all six light bands 

 extending across the whole wing) the fourth light spot (counted 

 from the wing-root), proceeds farther than the hind-limit of the 



1) Kurt Smolian, Ueber die Variabilitat des braunen Barenspinners und die 

 Beziehungen desselben zu den ihm nachstverwandten Arten, Jenaische Zeitschr. 

 f. Nat. Wiss. Vol. L, 1913. 



