2'i2 THE ENTOMOLOGIST. 



birds, and many others, nest inland, often amidst dense 

 vegetation; and lie believes they often carry seeds, attached 

 to their feathers, from island to island for great distances. In 

 the tropics they often nest on the mountains far inland, and 

 may thus aid in the distribution even of mountain plants. 

 Insects, on the other hand, are mostly conveyed by aerial 

 currents, especially by violent gales; and it may thus often 

 happen that totally unrelated plants and insects may be 

 brought together, in which case the former must often perish 

 for want of suitable insects to fertilise them. This will, I 

 think, account for the strangely fragmentary nature of these 

 insular floras, and the great differences that often exist 

 between those which are situated in the same ocean, as well 

 as for the preponderance of certain orders and genera. In 

 Mr. Pickering's valuable work on the 'Geographical Distri- 

 bution of Animals and Plants,' he gives a list of no less than 

 sixty -six natural orders of plants unexpectedly absent from 

 Tahiti, or which occur in many of the surrounding lands, 

 some being abundant in other islands, — as the Labiatae at the 

 Sandwich Islands. In these latter islands the flora is much 

 richer, yet a large number of families which abound in other 

 parts of Polynesia are totally wanting. Now much of the 

 poverty and exceptional distribution of the plants of these 

 islands is probably due to the great scarcity of flower- 

 frequenting insects. Lepidoptera and Hymenoplera are 

 exceedingly scarce in the eastern islands of the Pacific ; and 

 it is almost certain that many plants which require these 

 insects for their fertilisation have been thereby prevented 

 from establishing themselves. In the western islands, such 

 as the Fijis, several species of butterflies occur in tolerable 

 abundance, and no doubt some flower-haunting Hymennptera 

 accompan} them ; and in these islands the flora appears to 

 be much more varied, and especially to be characterized by 

 a much greater variety of showy flowers, as may be seen by 

 examining the plates of Dr. Seeman's ' Flora Viliensis.' 



Darwin and Pickering both speak of the great prepon- 

 derance of ferns at Tahiti; and Mr. Moseley, who spent several 

 days in the interior of the island, infarms me that " at an 

 elevation of from 2000 to 3000 feet the dense vegetation is 

 composed almost entirely of ferns. A tree-fern (Alsophila 

 Tahitensis) forms a sort of forest, to the exclusion of almost 



