THE TKACHEATION OF WLXGS 43 



connection (a. c-a) which passes mesad, just dorsad of the dorsal longi- 

 tudinal trachea (d. It), to anastomose with its fellow of the opposite 

 side. 



The changes in the costo-radial trachea to the hind wing have been 

 similar to those to the front wing. The anterior tracheal stem to the leg 

 (as) forms a common tmnk with the cubito-anal trachea of the front wing, 

 as has just been described, and then it continues dorsad, in common with 

 the costo-radial trunk (c-r) of the hind wing, until it becomes independent 

 of the wing trachea and passes ventrad to unite with the posterior stem of 

 the leg trachea (ps). 



The costo-radial trachea of the hind wing also has an accessory connec- 

 tion (a. c-r) with the dilated dorsal longitudinal trachea {d. It) . The cubito- 

 anal connection (cu-a) is unmodified except for a small accessory connection 

 between it and the anterior stem of the leg trachea (as) , similar to a 

 connection found in the mesothorax. 



The posterior stem (ps) of the trachea to the metathoracic leg (h) is 

 small and has new relationships at its point of entrance into the specialized 

 hind leg. The descriptions of the leg trachea in the metathorax, which have 

 given rise to these new relationships involving the second abdominal 

 spiracle, belong more properly to the last part of this paper and their dis- 

 cussion will be postponed for the present. 



The basal connections of the wing trachece of Anax and Lestes, Order 

 Odonota. — The tracheation of Plathemis lydia was described and figured by 

 G. G. Scott {Biological Bulletin 1905, ix : 341-354). The author described 

 the tracheae of the wing as arising from a loop, the anterior trachea of the 

 loop arising from the dorsal longitudinal trachea and the posterior trachea, 

 in the case of the mesothorax, arising from the short transverse connective 

 in such a way that the two posterior tracheae of the fore wings originate side 

 by side. The tracheation of the hind wings is described as similar to that 

 of the fore wings except that the anterior trachea arises from the spiracular 

 trunk near the dorsal longitudinal trachea and the posterior trachea is 

 described as originating directly from the dorsal longitudinal trachea. 



R.J. Tillyard {Proceedings of the Linnean Society of New South Wales, 

 1914, xxxix, pt. I, p. 163-216, pi. xi-xiii) made a study of Odonata n^nnphs 

 using transmitted light to distinguish the tracheae. His description is said 

 to embody the results obtained from the study of both the Anisoptera and 

 the Zygoptera and a diagram of the lateral view of the thorax is given to 

 show the connections of the wing tracheae. This author describes one 

 tracheal branch to each leg and one trachea, arising from the dorsal longi- 

 tudinal trachea, as entering each wing pad from the anal end, forming a 

 loop from which the wing tracheae arise, and passing out of the wing pad at 

 the costal end as a fine threadlike trachea which connects with the leg 

 trachea of the same segment. 



