260 ENTOMOLOGICAL NE\VS [Nov., '22 



It is noted too, that variability in the number of branches 

 also characterizes the radius and media in this primary stage. 

 In figs. 2 and 3, R is two-branched, while in fig. 1 it is nn- 

 branched. The media is five-branched in fig. 2, while in figs. 1 

 and 3 it is in its more usual four-branched condition. Finally 

 it may be noted that the posterior two tracheae are three- 

 branched in fig. 2, and that in figs. 1 and 3 they are two- 

 branched. In regard to the costa it might be mentioned that, 

 at least in Anax, this trachea almost always arises not from 

 the same tracheal trunk as do the other wing tracheae, but from 

 a branch of this trunk, the accessory costo-radial trunk, which 

 passes out of the base of the wing. This condition is seen in 

 figs. 2-8 ; in fig. 1 the costa arises from the same trunk as do 

 the other tracheae. In Gomphus, the costa arises either directly 

 from the transverse basal as do the other wing veins, or from 

 the accessory costo-radial trunk as it does in Anav. 



Returning to the radius and observing the course of its 

 branches in the earliest stages, we note that there is no crossing 

 of any branch of this trachea over any part of the media. In 

 fig. 1 the radius is not branched at all and is entirely remote 

 from the media. In figs. 2 and 3 the radius has two branches, 

 the posterior branch being, according to the view of Needham. 

 the radial sector. This posterior branch, which for the present 

 I will continue to refer to as Rs, is in this stage entirely free, 

 and remote from the media. This observation apparently 

 agrees with that of Needham, who illustrates such a condition 

 in his fig. 1, A, if we disregard the difference in the sizes of 

 the wings in the two cases. We must, however, remember that 

 the wing rudiments represented in figs. 1-3, are in a much 

 earlier stage of development than that figured by Needham 

 which, he states, was 1 mm. long, as is indicated by their 

 smaller absolute size, the difference in the proportions of length 

 to width and in the great variability in the arrangement and in 

 the number of branches of the various tracheae. 



Figs. 4-7 represent the tracheation of the wing rudiments 

 taken from Ana.r larvae whose body length was 13 to 13.5 mm. 

 These larvae are apparently of the instar following upon that 

 of the larvae just discussed, since on frequent collecting trips 



