212 PHILIP p. CALVERT. 



neons possession of the following structural features: for the imago, 

 the relatively less extent of the eyes, the less degree of fusion shown 

 in the labium, the completeness of the first lateral thoracic suture 

 (i. e. a less intimate union of meso- and nietathorax), and the dis- 

 tinctness of meso- and metathoracic ganglia ; for the nymph, a greater 

 resemblance to Ephemerine nymphs by the possession of three, origi- 

 nally setiform, caudal tracheal-gills, and of lateral abdominal tra- 

 cheal-gills {Euphcea). 



If this starting point be accepted, the Agrioninse, admittedly the 

 nearest allies of the Calopteryginae, form a group having no relation- 

 ship to the other subfamilies save by a common descent from Calop- 

 terygine ancestors. Approaches to connecting forms between the 

 two groups are furnished, as De Selys (40) long ago suggested, by 

 the exotic Calopteryginse Amphipteryx and Micromerus. Of the 

 Agrioninre, the legion Lestes stands nearest the Calopteryginje by 

 the point of origin of its subnodal and median sectors. The legion 

 Agrion is the most specialized of its subfamily ; of its genera, Argia 

 is probably the oldest phylogenetically, and the line of descent from 

 it may run through Agrion, Enallagma or Nehalennia, and Ischnura 

 to Anomalagrion. With such a phylogenetic series the views of 

 Kolbe (3) agree — that the male appendages, which are the essential 

 supports in copulation, gradually lose their relative size; that to 

 supply this deficiency emarginations and lobes are formed on the 

 hind margin of the prothorax of the female, and that in accommo- 

 dation to the shape of this last, the tenth segment of the male be- 

 comes emarginated or provided with bifid processes. 



Of living Anisoptera, the Gomphinie of the legion Petalura of 

 Selys most nearly approach the Calopteryginse in that they have 

 the eyes separated, the median lobe of the labium bifid, the vulvar 

 laminte formed as an ovipositor and with genital valves. We know 

 nothing of their nymphs. There are but four living genera, viz. : 

 Petalura with one species from Australia, Uropetala with one species 

 from New Zealand, Tachopteryx with two species from the United 

 States and one from Japan, and Fhenes with one species from Chili. 

 Four fossil species have been referred to Uropetala and three to 

 Petalura (Kirby 35). 



Derived from Petaluroid forms, three lines of descent may be con- 

 ceived. One of these is that of the Aeschninse which preserve the 

 ovipositor, the genital valves and the distinctness of meso- and meta- 

 thoracic ganglia, but in which the median labial lobe is entire, the 



