0.1331. 



DRAGON-FLY WING VENATION— NEEDHAM. 



729 



UNEQUAIJA' DEVELOPED WINGS IN THE SAME SPECIES. 



1. The speckdizaffon of fore and hind wings to an unequal degree^ 

 nhen hoth {or the parts concerned (f hoth) arefoUmovng similar lines.— 

 V single illii.stration of this will suffice. In Chalcopteryu' (fig. 22) 

 he fore wing has in several points outrun the hind. For instance, 

 ^ein M. separates from vein M^ in the hind wing at the subnodus, as 

 s usual: but in the fore wing i/^ has fused with M^ for the space of 

 eA^eral cells' length beyond the subnodus. Again, in the space 

 )etween veins 21^ and JT^ there are a number of interpolated sectors, 

 ill of which are independent of the veius in the hind wing, but in the 

 'ore wino- the next to the longest of these has become attached to vein 

 M^ in such position that M., now appears forked. It will be seen at a 



Fig. 22.— Wings of Chah-iipkri/.r riilHan.f Rambur. 



glance that the anterior branch of this fork is the same thing as the 

 independent sector occupying the same position and relations in the 

 hind wing. First, a broken line of crossveins became straightened 

 out longitudinallv to form the sector; then, one of the crossveins 

 lying below its proximal end in the fore wing became declined to 

 brat^ the sector against vein 3J,. But the bracing of the wing tip did 

 not stop with this. The upper branch of the fork has acquired a lesser 

 fork of its own, whose anterior branch is in like manner developed 

 out of a still shorter sector, which has remained independent in the 

 hind wing. Again, the longer of the two sectors in the space between 

 veins i^.^Tand Jf, in both wings become attached to vein M,; a (sym- 

 metrical fork has thus been developed in the fore wing, but in the 

 hind wing the adjustment is -still imperfect. 



