258 ENTOMOLOGICAL NEWS [Nov., '22 



in the development of the larval wing. These drawings are to 

 show: in fig. 1, A, the primitive condition in which the trachea 

 R s occupies its normal position anterior to ,1/1, in fig. 1, B. 

 the second stage, in which Ks has come to lie posterior to Ml 

 but is still anterior to M2, and finally, in fig. 2, the condition 

 obtaining in the full grown larva, in which Rs lies posterior to 

 M2. The occurrence of these stages in the larval wings con- 

 stitutes a part of Needham's evidence that the vein lying be- 

 tween A/2 and A/3 is the radial sector and is not a true branch 

 of the media. 



The work of Tilly ard (1922) has again thrown doubt upon 

 the identity of the vein Rs, for this author does not concur in 

 Needham's interpretation but states that the Rs of Needham is 

 really a branch of the media, although receiving its tracheal 

 supply in part through a branch of R; and that the original Rs 

 has been cut off by, and become attached to, the media. While 

 admitting that if the ontogenetic stages described by Needham 

 actually occur in the developing wing rudiments of the larva, 

 this would constitute strong evidence in favor of Needham's 

 view, Tillyard doubts that such stages can be demonstrated. 



It was suggested to me by Dr. Philip P. Calvert, that in view 

 of the doubts which had thus been cast upon the existence of 

 the two earlier stages described by Needham, it would be 

 desirable to go over the work of that author and examine the 

 tracheation of the earliest larval instars, since an accurate 

 knowledge concerning the condition of the trachea Rs at its 

 first appearance and of how it comes to occupy the position it 

 is said to assume in later instars might be of value in solving 

 the difficult problem of the homology of the imaghial vein Rs. 



The larvae examined were those of Anax jnnlns Drury, 

 Gomphus villosipcs Selys and GompJuts c.rilis Selys. The wing 

 rudiments of these larvae were prepared and mounted essen- 

 tially after the manner described by Needham. In the case of 

 the younger ones it was necessary, because of the small si/e 

 of their wings, to cut out the thoracic terga and the first seg- 

 ment of the abdomen in one piece and, without removing or 

 disturbing any of the underlying tissue, to mount the piece 

 thus removed entire. Treated in this way, the wing rudiments 



