Diptera.] 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



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obtained from such a small and localised part of the total area, it is very important 

 that the interior-dwelling forms be collected in the larger islands. Immigrant forms 

 will, doubtless, be introduced to some extent, and the alteration of the natural con- 

 ditions will cause considerable disturbance to the local species. Many species of 

 Diptera are extraordinarily local in their distribution, being sometimes confined to a 

 few square yards of favourite locality, and such localities are readily destroyed. 

 The coast forms are likely to be far less affected by settlement and cultivation than 

 the inland ones, and hence attention should be at once paid to the latter. 



Aetiology. — A remarkable feature of the collections was the abnormal number 

 of species with reduced wings. This is probably due in part to the method of collec- 

 tion, which would most likely favour the capture of species which were unable to 

 fly. It is, however, a feature in the Diptera of the southern islands. From Ker- 

 guelen Island we have had species described by Mr. G. H. Verrall (Phil. Trans. B.S.L., 

 extra vol., 1878) with greatly reduced wings. These belong to various families — 

 Calycopieryx moseleyi to the Micropezidae, Amalopteryx maritima and Apetenus 

 litoralis to the Ephydridae, and Anatalanta aptera to the Borhoridae ; the latter is 

 quite devoid both of wings and halteres. Becker has also recently described a Scato- 

 phila (Ephydridae), in the " Reports of the Swedish Antarctic Expedition," which 

 has greatly reduced wings. In the present paper species of reduced size are de- 

 scribed belonging to the families Dolichopidae, Anthomyiidae, and Phycodromidae. 

 Additional evidence is thus present for the correlation of this condition with the 

 existence of a very windy climate. 



The genera of Diptera are very cosmopolitan in their distribution, and, further- 

 more, collections of them are but scanty both in numbers and in material ; hence it 

 is not possible at present to draw any conclusions as to the regional relationships of 

 the species considered in this paper. 



My thanks are due to the following gentlemen for their kind help in regard 

 to certain critical points : Professor P. Stein, of Treptow, Pomerania ; Mr. G. H. 

 Verrall, F.E.S. ; and Mr. J. E. Collin, F.E.S., of Newmarket, England. 



DESCEIPTIONS OF NEW SPECIES. 

 LIMNOBIIDAE. 

 DiCRANOMYiA, Stephens. Cat. of Brit. Ins., ii, 243 (1829). 

 Dicranomyia annulata, sp. nov. 

 A pair belonging to this genus was sent from the Auckland Islands. They are 

 very much like the common European species, D. chorea, and do not agree with 

 the description of any of the forms hitherto noted from the Antarctic islands. 

 Length. — Body, 8 mm. ; wing, 9 mm. 



The heads are shrivelled, but apparently offer no particular characters. 

 Wings. — A spot on the praefurca at its origin. The stigmatical spot present, 

 and just fills the space from the marginal cross- vein to the forking-point of the radial 

 vein. The origin of the radial vein is slightly behind the end of the mediastinal. 

 The subcostal cross-vein is indistinct, and is just perceptibly before the origin of 

 the radial vein. The discal cell is closed. The veins have minute bristles, which 

 are most evident on the radial vein. 

 9—8. 



