210 PHILIP P. CALVERT. 



Lias, lithographic stone, Sieblos) and Stenogomphns (Roan Mountain). Cordule- 

 gaster occurs in the lithographic stone. Anax (Radoboj) and Aeschna (Scham- 

 belen, lithographic stone, Wardoiir, Queensland Cretaceous, Florissant, Oeningen, 

 Rott) are living Aeschninse. Radoboj and Monte Bolca have yielded the living 

 Cordtdia. Lastly, for the Libellulinse are the extinct Aeschnidium (Swanage. 

 lithographic stone) and Libellulium (Swanage, Wardour), and living " Libellula" 

 (English Lower Lias, lithographic stone, Provence, Auvergne, Oeningen, Schoss- 

 nitz, Rott). 



The oldest Odouate remains are therefore of the Gomphinaj, x\esch- 

 niii£e and Libellulinse from the Lower Lias. The Calopteryginse, 

 Agrioninae and Cordulegasterinse are first found in the Oolite. The 

 oldest known Cordulinse are of Eocene age. The value of this 

 paleontological evidence will be discussed later. 



4. Relationships of the Odonata. 

 relationships to other insects. 



The insects to which the Odonata are most nearly related, are the 

 Ephemerina and the Perlina. All three groups, besides passing 

 through an incomplete transformation, agree in the possession of 

 three ocelli, numerous Malpighian tubules, and of aquatic nymphs 

 which breathe by tracheal-gills. 



The Odonata and the Ephemerina constitute the Subulicornia of 

 Latreille, by reason of their short, subulate (awl-shaped) antennse; 

 other agreements are the relatively small size of the prothorax to 

 the other thoracic segments in the imago, but not in the nymph, and 

 the absence of a part which may be closed as a fan in the hind 

 wings — characters which are the opposite of those of the Perlina. 

 The three terminal jointed setse of the Ephemerine nymphs, clothed 

 with short bristles, recall the three caudal, though jointless,* tracheal- 

 gills of the nymphs of the Zygoptera, which at hatching are setiform 

 and sparsely hairy, and in the Calopterygine genus Euphcea, remain 

 setiform and hairy for at least the apical half of their length. The 

 nymphs of Euphcea also have a lateral gill on each side of abdominal 

 seo-ments 1-8, another resemblance to the Ephemerine nym})hs in 

 which such gills exist on 1-7. But in almost all other respects the 

 Ephemerina differ from the Odonata in that their imagos have their 

 mouth-parts more or less atrophied and functionless, the tarsi four- 

 or five-jointed, the wings of unequal length, the venation different, 

 the terminal abdominal appendages (setse) jointed, and want the 

 characteristic separated accessory genital organs of the male Odonata. 



*- Nymphs of Lestes show traces of an articulated structure in the stems of the 

 caudal tracheal-gills. 



