871 



FURTHER RESEARCHES UPON THE PROBLEMS OF 

 THE RADIAL AND ZYGOPTERID SECTORS IN 

 THE WINGS OF ODONATA, AND UPON THE 

 FORMATION OF BRIDGES. 



By R. J. TiLLYARD, M.A., B.Sc, F.L.S., F.E.S., Linnean 

 Macleay Fellow op the Society in Zoology. 



(Six Text-figures.) 



My previous studies upon the problem of Dragonfly wing- 

 venation (2, 3) have conclusively shown that the sub-Order 

 Zygoptera diifers from the Anisoptera in possessing no sector to 

 the radial trachea. The latter is straight and unbranched in 

 the Zygoptera. The place occupied by Rs in the Anisoptera, 

 viz., between M„ and M^, is filled in the Zygoptera by an addi- 

 tional trachea branching off from M. This I have termed the 

 Zygopterid sector, Ms. As the imaginal wing-venation has to 

 be interpreted by means of the precedent tracheation of the 

 larval wing-sheath, I have logically applied the same terms to 

 the venation. 



Now, in a former paper (2), I indicated one genus, Neosticta, 

 which might possibly prove an exception to the above rule. In 

 the wings taken from a larva of this genus, I thought that I 

 could distinguish a true trachea Rs. The pigmentation of the 

 wing-sheath, however, was so dense, and the specimen so far 

 advanced towards metamorphosis, that the decision had to be 

 held in suspense, pending the discovery of more material. Since 

 that time, I have carefully examined a large number of larval 

 wings of genera belonging to all three Zygopterid families 

 {Calopterygidce, Lestidce, and Agrionidce) without discovering a 

 single exception to the rule stated above, viz., that R is un- 

 branched in Zygoptera. Thus it became more than ever im- 



