222 PROCEEDINGS OF THE ACADEMY OF [May, 



Two Neotropical genera occasionally present similar features to 

 those observed in Chlorolestes. The Godman-Salvin Collection of 

 Central American Odonata, now in the British Museum, includes 

 the type and three other specimens of Paraphlebia quinta Calv., all 

 from Guatemala. Two of these have an additional antenodal in as 

 many as five out of their eight wings, and in each instance it is 

 proximal to the first regular antenodal and is restricted to the sub- 

 costal space. A 9 of Heteragrion chrysops Hag., from Vera Cruz, 

 also in the Godman-Salvin Collection, has, in three of its wings, a 

 supernumerary antenodal between the usual ones and limited to the 

 costal space. 



All the recent species which have been considered so far belong to 

 De Selys' Legion Podagrion, a group which has been declared to be 

 "heterogeneous and untenable," but which includes the most archaic 

 genera of Agrioninae that have yet been made known. However, 

 at least two species belonging to the more highly specialized genera 

 may be cited as affording other instances of the accidental reappear- 

 ances of the kind under review. One of these is the type 9 of 

 Ischnura granti McLach., from Sokotra, preserved in the British 

 Museum, in which a third antenodal is present in all the wings, except 

 the right fore- wing. In each case it is placed beyond the level of the 

 arculus and ends on the subcosta. The other species referred to is 

 Pyrrhosoma nijmphula Sulz., concerning which Prof. Philip P. Calvert 

 is kind enough to inform me that he possesses a 9 from Birmingham, 

 Warwickshire, taken by Mr. W. H. Bath, whose left fore-wing has 

 three antenodals, the third lying beyond the usual two and crossing 

 the costal space only. 



It is not improbable that the supernumerary antenodals which we 

 have found to occur sporadically, as an individual peculiarity, repre- 

 sent nervures which were present normally in the wings of some 

 ancestral form, but which have been lost in the majority of living 

 Agrioninae. The main tendency of Agrionine development has been 

 in the direction of simplified wing-venation, and in the more highly 

 specialized genera the costal and subcostal spaces have shared in the 

 general elimination of superfluous cross-veins. As soon as the 

 number of antenodals had been reduced to two, however, specializa- 

 tion in this direction appears to have ceased, for no Agrionine is known 

 having fewer than two complete cross-veins, except in rare cases of 

 individual aberration. In this connection it will be useful to quote 

 some remarks made by Prof. Calvert respecting two Mexican speci- 

 mens of Ischnura denticollis Burm., which are in the following terms: 



