344 Annals Entomological Society of America [Vol. VI,. 



diverges toward the costal border. Radius occupies a 

 somewhat similar position in Myndiis (Fig. 47), except that 

 there are three or four small branches near the tip and the 

 trachea does not coalesce with medius in any part of its course. 

 The condition of the radial trachea in Dictyophara (Fig. 25), 

 is almost identical with that in Myndus, except that there 

 are small lateral branches toward the tip. In Thionia (Fig. 

 27) and Scolops (Fig. 23), the radial trachea is quite similar in 

 appearance to that in the genera discussed above except that sep- 

 arate veins are formed along these two trachea in Thionia. In 

 both of these genera the lateral branches near the tip are much 

 weaker and more uncertain in their position and are not the 

 fore-runners of typical and fairly constant longitudinal veins, 

 but of rather uncertain cross veins which are fairly common 

 in these genera. In Amphiscepa (Fig. 5), and Acanalonia 

 (Fig. 1) radius is a single unbranched trachea. In Ormenis 

 (Fig. 3), the radial trachea consists of two main tracheae which 

 separate into several smaller branches before reaching the 

 tip. 



The Medius of the Fore Wing. 



In all the genera studied the medial trachea is the most 

 important trachea of the fore wing and its branches occupy 

 more area than the branches of any other trachea. In the 

 genera studied medius seems to be typically four branched 

 only in Amphiscepa (Fig. 5). Each one of these branches, 

 however, branches one or more times before reaching the tip 

 of the wing. In Ormenis (Fig. 3), medius divides into twO' 

 branches each branch again dividing into two branches. Each 

 of these branches, however, is several times divided before 

 reaching the tip of the wing pad. In Acanalo?iia (Fig. 1), 

 medius is three branched, these branches representing medius 

 one, medius two and medius three plus four. In Scolops 

 (Fig. 23), Dictyophara (Fig. 25) and Thionia (Fig. 27), medius 

 is typically two branched, although these branches may divide 

 one or more times before reaching the tip of the wing pad. 

 The veins which form along these secondary branches are not 

 at all constant in position and relative importance. In Stobcera 

 (Fig. 45), medius divides into two main branches. These 

 branches represent medius one plus two and medius three 

 plus four, medius one and medius two separating before reach- 



