106 Annals Entomological Society of America [Vol. VI, 



THE SUBCOSTA OF THE FORE WING. 



The subcostal trachea in the Jassidce is very anomalous. 

 It reaches its greatest length, in the genera examined, in the 

 genus Jassus (Fig. 60), where it passes beyond the apex of the 

 wing and replaces R2 and R3 in the ambient vein. Subcosta is 

 slightly shorter in Gypona (Fig. 8), of about the same length in 

 Spangbergiella (Fig. 20), also in Agallia (Fig. 1). In Acinop- 

 terus (Fig. 41) it is still shorter barely reaching R2. In Platy- 

 metopius (Fig. 26) it is about half the length of the main stem 

 of Radius. No further evidence of the presence of Subcosta 

 was found although the Subcostal vein on the border of the wing 

 is well developed in all of the adult wings which the writer has 

 examined and it shows very clearly as a distinctly lighter area 

 in all the older nymphs examined. This series undoubtedly 

 shows how the subcosta has atrophied in Jassidae. 



THE RADIUS OF THE FORE WING 



The radial trachea in the fore wing of Jassidce is typically 

 two-branched although in some forms three and even four 

 branches do occur. The two branches of the typical radius 

 represent R2+3 and R4+5. Ri has almost completely disappeared 

 from the fore wings of the Jassidce. It does occur, as a delicate 

 branch, in a few genera but gives rise to a very characteristic 

 cross vein between subcosta and radius which is known cur- 

 rently as the "nodal vein". The nodal vein, however, is a 

 very anomalous one and its characters will be discussed later. 

 Ri has been found in the following widely separated genera, 

 Oncometopia (Fig. 3), Scaphoideus (Fig. 44) and Typhlocyba 

 (Fig. 64). In other genera there remains a distinct cross vein 

 connecting subcosta with the main stem of radius, or subcosta 

 with R2+3. This vein, which is usually referred to as the nodal 

 vein, undoubtedly represents the remnant of Ri or R2. Or it 

 may be considered as a vein which merely followed a weak 

 lateral branch of R or R2+3, which either happened to be con- 

 nected with the main stem of radius, when it resembles Ri, or 

 it may have happened to be connected with R2+3 in that case 

 it resembles R2. The writer is inclined to think that this is a 

 distinct vein representing in some cases Ri and in others R2. 



Trachea Ri is very conspicuous in Oncometopia (Fig. 3), 

 Scaphoideus (Fig. 44) and Typhlocyba (Fig. 64). The resulting 



