84 



Joh7i Henry Cmnstock 



I was led to make a careful study of this part of the wing 

 by the discovery that in Hepialis an entirely different method 

 of uniting the two wings of each side has been developed. In 

 this genus, and as I have since discovered in Micropteryx 

 also, instead of the wings being joined by a frenuhim, which is 

 a bristle or a bunch of bristles borne by the hind wing, they 

 are joined by a membranous lobe extending back from near 

 the base of the inner margin of the fore wing (Fig. 27, 28, j). 



To this lobe I have applied the name J jigufn. 



When the wings ol Hepialis are extended, the jugum pro- 

 jects back beneath the costal border of the hind wing, which, 



in. 



viii viijvn, ^3 * 



Fig. 28. — Micropteryx. 



being overlapped by the more distal portion of the inner mar- 

 gin of the fore wing, is thus held between the two, as in a 

 vice. 



The discovery of the fact that there are two distinct modes 

 of uniting the wings during flight suggests the inference that 

 in the primitive Lepidoptera the wings were united in neither 

 way. For it is not easy to see how one mode could have been 

 developed from the other. 



It is probable that in the primitive moths the mesothorax 

 and metathorax were much more distinct than in the recent 

 forms ; and consequently the two pairs of wings were farther 



