NA THALIS.— DISMOEPHINA. 173 



Nathalis iole is common in the South-western States and California, and thence 

 spreads southwards over nearly the whole of the mountainous parts of Mexico and 

 Guatemala. Its range in altitude is considerable, and extends from about 1500 feet 

 above the level of the sea to 7000 or 8000 feet. It is found in open places, where it 

 frequently associates with species of Terias. 



Both sexes are subject to some variation, which chiefly affects the dark band parallel 

 to the inner border of the primaries. In some specimens this band is evanescent, in 

 others strongly defined. 



Group DISMORPHINA. 



Subcostal nervure of primaries four-branched ; tegumen of the male furcate. 



Dismorphia and its allies offer so many points of distinction from the rest of the 

 Pierinae that it seems advisable to place them in a separate section or group. The 

 secondary sexual organs of the male, though closely resembling one another as described 

 below, differ materially from all the other members of the Pierinae we have examined. 



The secondaries in the females of every member of this section, and in the males 

 in nearly every case, have the subcostal branch emitted some distance beyond the cell. 

 The structure of the antennae presents the greatest peculiarity. Each of the seven or 

 eight joints forming the distal end of the club have four round depressions surrounding 

 their distal edge, which we take to be sensory pits, a structure more complicated than 

 we have yet found in any other group of the Pierinae, though Terias possesses a ventral 

 series of similar depressions. Another peculiarity of this section is the cretaceous patches 

 on the underside of the primaries, and the upperside of the secondaries being surrounded 

 with a smooth silky area, which Doubleday describes as composed of exceedingly minute 

 and peculiarly-formed scales. These latter do not exceed the six hundred and fiftieth part 

 of an inch in breadth or the four hundredth of an inch in length ; they are heart-shaped, 

 deeply lobed at the base, more or less rounded at the apex, varying a little in the pro- 

 portion of length to breadth ; the lobes at the base project beyond the little foot-stalk 

 by which they are attached to the wing, which has its origin at the deepest part of the 

 notch between the lobes. Each scale is therefore bent to allow of its attachment to the 

 wing; the chalky spot in the middle of this silvery patch is composed of scales of 

 ordinary form, more erect and more imbricate than is usually the case. 



The posterior wings are in most cases extraordinarily developed, and in this respect 

 have no parallel in other Pierinae. 



The Dismorphina are peculiarly tropical American, and there is nothing like them 

 in any portion of the Old World. 



Doubleday and the older writers, deceived by the resemblance of the pattern of the 

 wings of several species of Dismorphia to that of certain Heliconinae, considered that 

 there might be a real relationship between these insects. The fully-developed front 



