NO. 2 THORACIC MECHANISM OF A GRASSHOPPER — SNODGRASS ^J 



The forewing (fig. 45 A) has a broad anterior, or costal, area in 

 which there is no vein represented by a costal trachea in the nymph 

 (fig. 46 A), though the anterior margin is strengthened by a vein-like 

 thickening. The first vein (fig. 45 A, C) is evidently the costa branch- 

 ing from the siihcosta (Sc), though the common basal stalk has the 

 usual relation of the subcosta to the first axillary sclerite (fig. 47 A, 

 I Ax). The next vein (R) is unquestionably the radius, as shown by 

 its distal branches and by its basal connection with the second axillary 

 (fig. 47 A, 2Ax). The media (M) is united proximally with the 

 radius and with one of the median sclerites of the wing base (w'). 

 The first long vein following the media is a two-branched cubitus 

 (iCti), between which and the basal part of the media is the inter- 

 calary vein (/). Then comes an unbranched vein, here designated 

 2Cu, lying close before the anal fold (AF), and finally a group of 

 three veins (A) connected basally with the third axillary, or flexor 

 sclerite of the wing base (fig. 47 A, sAx). 



If we identify the " anal veins " as those veins lying posterior to 

 the anal fold and connected basally with the third axillary, there are 

 then but three anal veins in the forewing of Dissosteira (fig. 45 A, 

 A, fig. 47 A, I A, 2 A, 3A). An incomplete vein (fig. 47 A, s) lying 

 just behind the anal fold (AF) is apparently a secondary vein. The 

 vein immediately before the anal fold (^Cu) is the " first anal " of the 

 Comstock-Needham system, but probably it is the vein regarded as a 

 part of the cubitus by Tillyard (1919) and others, designated Ciiz by 

 Tillyard and cubital sector by Karny. In Dissosteira the vein in ques- 

 tion has no basal connections and is here termed the second cubitus 

 (2Cu). It clearly belongs to the cubital area of the wing. In the nym- 

 phal wing of an acridid, as illustrated by Comstock and Needham (fig. 

 46 A), tracheal precursors of the cubitals are not evident, since the 

 final group of three tracheae springing from a common basal stem 

 would appear to represent the group of three anals in the adult wing 

 (fig. 45 A, ^ ) . According to Comstock ( 1918) , however, the first vein 

 of this group is the "cubitus" (fig. 46 A, Cm), and the second the 

 "first anal" (lA). The identity between the nymphal tracheae and 

 the adult veins in the forewing is certainly not clear, and no solution 

 of the problem can be offered here. 



The vein tentatively called " second cubitus " in this paper (figs. 

 45 A, 47 A, 2Cu) is, by nomenclatural priority, the true anal vein, 

 and the name " anal," though a poor designation, should be retained 

 for it, while a new term should be devised for the veins lying posterior 

 to the anal plica associated with the third axillary sclerite. The fan- 



