302 ENTOMOLOGICAL NEWS [Dec., '22 



appears it is at first a single strand and not until the following 

 instar does it acquire a fascicled condition as the result of the 

 formation of parallel branches. Therefore, I believe that the 

 branch Rs, which appears in the instar shown in figs. 4-7 of 

 Anax, and in figs. 13 and 14 of Gomphus, is a new tracheal 

 outgrowth appearing first in this instar and that it is not the 

 posterior branch of the two-branched radius of the preceding 

 instar (figs. 2, 3, 9, 11, 12). This posterior branch of R 

 (called Rs by Needham) really develops into Rl, while the 

 original R\ of this first stage does not develop into any prin- 

 cipal trachea, but the small branches of which it is composed 

 pass forward into the region of the costal vein. 



I believe the evidence I have given is sufficient to demon- 

 strate that if the trachea which Needham refers to as Rs in 

 his fig. 1, A, is the true Rs, then in the grown larva the trachea 

 Rl is really Rs, and the Rl of Needham's figure is represented 

 in later stages only by the fine tracheae which pass forward and 

 supply the costa, or possibly it has become combined with Rs 

 and the fine tracheae going to the costal vein represent branches 

 of Rl. 



I have also shown that the tracheal branch of R which 

 crosses 71/1 and M2 is not the original posterior branch of this 

 vein which is seen in the first stage and which, according to 

 Needham, has undergone a shifting in position, but rather that 

 it is a new outgrowth of the radius and that in the instar in 

 which it first appears it is already in the position which it 

 occupies in the full grown larva. This trachea therefore, can- 

 not be considered as representing Rs in the sense that it has 

 developed by a shifting of the posterior branch of R which is 

 observed in the earliest stage and which Needham has said 

 must be Rs. 



This study of the tracheation of the wings of two Anisopter- 

 ous larvae has thus yielded not the slightest evidence that the 

 trachea Rs of the earliest instar has undergone a shifting in 

 position and has come to lie posterior to .1/2; but rather it has 

 shown that this trachea retains its original position and forms, 

 at least in part, the Rl of the grown larva. It has revealed that 



