THE WINGS OF LEPIDOPTERA 



327 



Fig. 335. — Wings of a hepialid, Pielus labyrin- 



theciis, seen from below. a, abnormal 



accessory vein. 



The suborder Frenats includes the greater part of the Hving Lepidop- 

 tera. Within this suborder are found great differences in the form of the 

 wings, in the details of wing-venation, and in the manner of uniting the 

 fore and hind wings. But, 

 in spite of this, it is a very 

 homogeneous group; all of 

 the variations in the struct- 

 ure of the wings are modi- 

 fications of a common type, 

 which is represented by 

 living members of the sub- 

 order. 



{e) THE WINGS OF THE 

 JUGATE 



In the wings of the 

 Jugatae the posterior lobe of 

 the fore wing is a slender, 

 finger-like organ, the jugum, 

 which aids in uniting the 

 fore and hind wings; and 

 the venation of the fore and 

 hind wdngs is quite similar, the radial sector of the hind wing being four- 

 branched, like that of the fore wing. 



The jugum. — The jugum is a peculiar type of the posterior lobe of the 

 fore wing that is found only in the Hepialidse. It is slender and projects 

 beneath the costal margin of the hind wing. As the greater part of the 

 inner margin of the fore wing overlaps the hind wing, the hind wing is held 

 between the two. This is shown in Figure 335, which represents the wings 



of one side seen from below. 

 The jugum is behind one of 

 the two principal branches of 

 the third anal vein, which may 

 be designated as vein 3dAi,and 

 is supported by the second of 

 these two branches, which may 

 be designated as vein 3dA2 

 (Fig. 336). 



The tracheation of the wings of pupae. — The tracheation of the wings of 

 pupa) of Hepialus thulc was studied by Dr. A. D. MacGillivray ('12), who 

 gives figures showing the courses of the tracheae in the forming wing-veins 

 of both the fore and hind wings. This is the only paper that has been 

 published on the tracheation of the pupal wings of a member of the Jugatae. 



Fig. 336. — Jugum of a hepialid. 



