294 ZOO-GEOGRAPHICAL DISTRIBUTION [CH. 



together with the total absence of Gomphinae (except Ictinus 

 australis). 



Tasmania. This island is poor in Odonata, though rich in large 

 rivers. Most of the Dragonflies are still-water forms. This 

 suggests that the fauna chiefly crossed from Australia at a time 

 when the land-connection (Bassian Isthmus) was too small to 

 carry many running rivers, and only possessed isolated ponds or 

 shallow lagoons [174]. 



New Zealand. This isolated province is very poor in all 

 forms of insect life. There are only eight known species of Dragon- 

 flies, comprised in the seven genera Uropetala, Aeschna, Somato- 

 chlora, Procordulia, Diplacodes, Austrolestes and Xanthocnemis. 

 Of these, the first and last are peculiar to the island. 



For an interesting comparison of the faunas of the three main 

 southern land-masses of Australia, S. Africa, and S. America, the 

 reader is referred to the introduction in Ris [136]. 



Fig. 154. Fore-wing (20 mm.), and portion of hind-wing of Lestoidea 

 conjuncta Tillyard, <J, Queensland. Original. 



Polynesia. 



Polynesia comprises all the islands (of non-continental origin) 

 lying in the Pacific Ocean eastwards from the boundary of the 

 Australian region. The principal groups are the Marshalls, 

 Gilberts, Tonga, Samoa, the Marquesas, Tahiti, and the Hawaiian 

 Islands. The interesting fauna of the Hawaiian Islands has 

 been fully dealt with by Perkins [H4-ii6j. There are two peculiar 

 genera, Nesogonia (Libellulinae) and Megalagrion, besides a large 

 number of species referred to the genus Agrion, whose larvae 

 live in water collected at the bases of the leaves of plants, and 

 possess reduced caudal gills. 



The non-continental character of the fauna of the Polynesian 

 Islands is shewn by the absence of all subfamilies except Aeschninae, 



