248 PROCEEDINGS OF THE ACADEMY OF [May, 



and Amphipteryx, have respectively 23-26 (front wing), 21-23 (hind 

 wing), and 7-10 (front wing), 7-8 (hind wing) antenodals. The 

 paleontological evidence (with the exception of Protomyrmeleon, 

 which has but one antenodal), including Steleopteron, is favorable to 

 the view that reduction in the number of antenodals is a more recent 

 acquisition. The preceding paper by Mr. Campion^^ discusses in a 

 suggestive way the apparent evidence for such reduction afforded 

 bj' recent Agrioninae. 



3. The Number of Postnodal Cross-veins. — Prof. Needham has 

 concluded®^ that one of the developmental tendencies of the Odonata 

 is: "Antenodal and postnodal cross- veins becoming reduced in 

 numljer, stronger, more regular, sometimes matched in position or 

 differentiated among themselves." In the Zygoptera this tendency 

 is more evident in the antenodals than in the postnodals, the latter 

 never becoming so few, absolutely, or relatively to the antenodals, 

 as in certain Anisoptera, e.g., Pachydiplax (front wing: antenodals 6, 

 postnodals 6) or Miathyria simplex (front wing: antenodals 7, post- 

 nodals 5). 



In the Protodonata, owing to the great extension of the subcosta 

 toward the apex of the wing, although there was no nodus, the 

 potential postnodals were less numerous than the actual antenodals, 

 assuming that the nodus of the Odonata developed at, or but little 

 proximad to, the apex of the subcosta. AVith retraction of the nodus 

 a greater number of postnodals in the costal space became possible. 

 Numerous cases of subsequent reduction in the number doubtless 

 occurred independently of each other, but the paleontological data 

 are not sufficiently abundant to demonstrate progressive reduction 

 in any one line of descent, however likely this may appear from the 

 standpoint of mechanical advantage or of economy of vein-forming 

 material. 



4. The Pterostigma. — The stigma is an Odonate feature not pos- 

 sessed by the Protodonata. In those Anisozygoptera, which are 

 considered by Handlirsch®^ to be ancestral to the Calopterygidae, 

 viz., the Tarsophlebiidse, the stigma was fairly oblique and in one 

 species at least braced at its proximal end.^^ 



In EuphcBopsis, of the Jurassic, the stigma is not oblique; in 



^ The Antenodal Reticulation of the Wings of Agrionine Dragonfiies. This 

 volume of these Proceedings, anted, pp. 220-224. 

 ^ Genealogic Study, p. 730. 

 65 Foss. Ins., p. 468. 

 ^.Tarsophlebia eximiaoi the .Jurassic; Handlirsch, I.e., Taf. XLVII, fig. 1. 



