. The biology of dragonflies (Odonata or Paraneuroptera). Dragon-flies. 298 ZOO-GEOGRAPHICAL DISTRIBUTION [CH. The Oriental Region. This is the least isolated of all the regions of the earth, being penetrable from each of the other three regions of the Old World. Palaearctie genera are excluded on account of the great rise in the mean annual temperature south of the barriers. From Ethiopia, the region has received species of , Urotheniis, and LibeUago. There remains Wallace's Line. Here we have a case closely parallel with that of the Isthmus of Panama. A large number of tropical Orien
. The biology of dragonflies (Odonata or Paraneuroptera). Dragon-flies. 298 ZOO-GEOGRAPHICAL DISTRIBUTION [CH. The Oriental Region. This is the least isolated of all the regions of the earth, being penetrable from each of the other three regions of the Old World. Palaearctie genera are excluded on account of the great rise in the mean annual temperature south of the barriers. From Ethiopia, the region has received species of , Urotheniis, and LibeUago. There remains Wallace's Line. Here we have a case closely parallel with that of the Isthmus of Panama. A large number of tropical Oriental genera have penetrated eastwards into the Australian region, but very few of the Australian forms have passed westwards into the Oriental. We note especially Hemicordulia and Diplacodes, which have spread far and wide beyond their Australian i;oocentres; the genus Argiolestes, which appears to have passed just across the barrier; Protorfhemis, Nanno'phya, and Fig. 155. Wings of Agrionoptera insignis allogenes Tillyard, ,^, Queensland. (Hw. 26 mm.) Original. The Australian Region. This is only now penetrable across Wallace's Line, by strong-flying species. There is evidence, however, of a separate immigration stream into the Australian continent via Timor, at some not very remote period, as well as some indication of the remains of an original Antarctic fauna driven northward through Tasmania. Australia proper, as dis- tinct from the Papuan sub-region, has a rich Gohijihine fauna, which seems certainly to have entered long ago via Timor, since Gomphinae (other than Ictinus) do not occur in Papua. The presence of Diplacodes nebulosa, Orthetrum fruinosum, Zyxomma fetiolatimi and other species on the mainland points in the same direction. The following genera have penetrated into Papua and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations m
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