with some remarks ebbend the Classification of the Diptera. 71 



The section Limnobina is a very compact group; I mean to 

 say that the great variety of forms, which belong to it, are evidently 

 adaptations to certain, as yet unknown, conditions of life; in the 

 essential characters, on the contrary, there is a remarkable agreement. 

 Often transitions may be found, or may be reasonably expected, 

 between the normal type and the most aberrant forms. The normal 

 types are Dicranomyia and Limnobia (sensu stricto), represented 

 by numerous species in the temperate regions of the old and the new 

 world, and also in Australia. Phipidia is a Dicranomyia, but 

 with pectinate antennae. Sometimes these antennae are, instead of 

 pectinate, only moniliform in the female, sometimes even in both 

 sexes, and thus come ncar the antennae of Dicranomyia. Gera- 

 nomyia is likewise a Dicranomyia with the parts of the mouth 

 elongated, and, as a consequence, with the palpi reduced in size. But 

 there are gradations in the length of the proboscis, as well as in 

 the size of the palpi. I possess a Dicranomyia from New Zealand, 

 with a longer proboscis than usual; and Mr. Skuse has even establi- 

 shed new genera on such variations of the proboscis and of the palpi 

 of Geranomyia in Australia (Skuse, Tip. brevipalpi in Proc. 

 Lin. Soc. N.S.W. Sept. 1889). — In other respects, the Organization 

 of these three genera is the same; the venation, and especially the 

 characteristic male forceps, belong to the same type, and all these 

 genera, in aecordance with the formula of their section (compare 

 above) have neither spurs, nor empodia, 



In tropical countries the original type of the section Limnobina 

 is sometimes modified in the most extraordinary manner, especially 

 in the shape of the wings and the venation. It becomes almost un- 

 recognizable and may deeeive the most experienced eye. Here the 

 index-characters, like sentinels, are invaluable. There is the South- 

 American genus Peripher optera Schiner, Novara, p. 47 (compare 

 about it my Studies on Tipulidae, II, Berl. Ent. Zeitschr. 1887, p. 174). 

 In this genus the proximal half of the wings becomes enormously 

 developed, in consequence of which, the whole wing assumes a different 

 shape. Minute cells, near the root of the wing, which generali)- are 

 not noticed at all, and have no name in the nomenclature, acquire 

 here a great dcvelopment; in P. ineommoda O.S. (Vienna Mus.) they 

 oecupy the whole proximal half of the wing. But the degree of this 

 dcvelopment is variable; it ditfers in different species, and is less 

 apparent in the female. In one case the diminution of such a de- 

 velopment was so great that in a speeimen before hihi Schincr did 

 not recognise bis own genus Peripheroptera and placed a female of 



