THE PUPAL WINGS OF HEPIALUS THULE. 
By ALex. D. MAcGILLIvray, 
University of Illinois, Urbana, I1linois.* 
The adult wings of the different species of the genus Hepialus 
are of particular interest because they show such a generalized 
condition. They approximate the closest to the hypothetical 
wing type of Comstock and Needham of any insect’s wings with 
which I am acquainted. This hypothetical type is supposed to 
show the number and arrangement of the longitudinal veins as 
they existed in the primitive insect’s wing. These authors have 
shown that a study of the arrangement of the trachez preceding 
the formation of the veins in developing wings throws much 
light on the homology of the veins of the adult wing. Many 
developing wings of Lepidoptera have been studied and figured, 
but so far as | am aware no investigator has studied and figured 
the developing wing veins of a species of Hepialus. It was my 
good fortune, through the kindness of Professor J. M. Swaine 
of MacDonald College, Quebec, Canada, to obtain pup of 
Hepialus thule hardened in formol in the right stage for a study 
of the developing wing veins. These specimens showed not 
only the trachez, which are represented as black lines on the 
accompanying figure, but also the veins, which are represented 
as white bands. Unfortunately nothing could be determined 
as to the arrangement of the tracheez after they left the veins 
and entered the body. The various veins will be taken up 
in order. et 
Costa.—The costa can be traced as a distinct, unbranched 
vein in both wings a short distance within the costal margin. 
A trachea was found only in the costa of the front wings and 
this was only a mere stub. 
Subcosta.—The subcosta shows as a two-branched vein, 
identical in form with the subcosta of the hypothetical type. 
The tracheal stem of subcosta is distinct and in the front wing 
branched midway between the base of the wing and the point of 
separation of subcosta into Sc; and Secs, though in the hind 
wings the point of branching of the trachea is much nearer the 
point of separation of the two branches of subcosta. The 
*Contribution from the Entomological Laboratories of the University of 
Illinois, No. 30. 
239 
