XV] ZOO-GEOGRAPHICAL DISTRIBUTION 297 



region. From the Oriental, it is probable that a considerable 

 list of Libelluline genera could be drawn up which have reached, 

 in China, beyond the somewhat arbitrary boundary of the 

 Yang-tse-kiang Valley. Southern Japan has also received a 

 fairly rich Oriental fauna, among which we must notice especially 

 the very striking genera Epophthalmia and Azuma (Macromiini), 

 and representatives of the genera Ictinus, Davidius, Gynacantha, 

 Lyriothemis, Rhyothemis, Pseudophaea, Neurobasis, Copera, Ceri- 

 agrion, Pseudagrion. The widely spread Diplacodes trivialis also 

 reaches into Japan. A single species of Argia (A. kurilis) has 

 colonized the Kurile Islands from Nearctica. 



The Ethiopian Region. It is very difficult to determine what 

 is the true ectogenic fauna of this region. Though it is now 

 almost completely shut off by desert from Palaearctica, and by 

 a wide stretch of sea from the Oriental region, yet there is a great 

 deal of evidence to shew that not so very long ago Odonata passed 

 quite easily from both these regions into Ethiopia. Though 

 I have included in the entogenic fauna a large number of Gomphine 

 genera which are very closely related to Onychogomphus or to 

 Gomphtis, it might very fairly be argued that these genera actually 

 form a very considerable invasion of essentially Palaearctic forms. 

 Such a conclusion is strengthened by the fact that Ethiopia has 

 no entogenic genera of Aeschninae except Hemianax. The only 

 difference is that the Gomphine settlement is the older of the two. 

 Are these Gomphine genera sufficiently differentiated from their 

 parent stock to merit the term "entogenic"? That question 

 cannot be answered except by someone far more familiar with 

 the Ethiopian fauna than myself. 



From Palaearctica, the region has received Platycnemis, 

 Agrion, Anax imperator, Sympetrum fonscolombei and Lestes 

 barbarus. From the Oriental, we notice the following genera: 

 Heliaeschna, Anaciaeschna, Hemicordulia (reaches to Madagascar), 

 Tetrathemis, Agriocnemis, and the widely spread Anax guttatits, 

 Diplacodes trivialis and Ischnura senegalensis. The close parallelism 

 between certain Ethiopian and Oriental genera, and the large 

 number of dientogenic genera common to the two regions, suggest 

 that a close connection formerly existed between them, via Mada- 

 gascar, Mauritius and the Seychelles. 



