DICRANOMYIA. 57 



although it may be principally at home in the more temperate 

 latitudes. D. vicarians from Aukland and D. morionella from 

 S. America, have been described by Dr. Schiner in the Reise d. 

 Novara, etc., Diptera, p. 46. The Limnobise fumipennis, 

 chorica, segrotans, and gracilis from New Zealand, mentioned in 

 Walker's List of Dipt. Brit. Mus., are all Dicranomyia. The 

 genus Ataracta, found in amber (Loew, Bernst. u. Bernstein- 

 fauna) is apparently synonymous with Dicranomyia. 



This genus is very closely allied to Limnobia, still the differ- 

 ences between them are numerous. They consist : — 



1. In the structure of the body : The feet of Dicranomyia 

 are generally more slender ; the ungues have usually but one 

 distinct tooth, whereas in Limnobia there are several ; the male 

 forceps in the two genera has a different structure. As to the 

 latter point, however different the two forms may be, I look upon 

 them as modifications of the same plan of structure, the whole 

 difference consisting in the more or less development of the fleshy 

 lobes. If we represent to ourselves the large fleshy lobes of Dicra- 

 nomyia lessened, the rostriform horny appendage, being closely 

 applied to the falciform appendage (marked b on the figures of 

 Tab. Ill), will form the double horny hook of Limnobia. Inter- 

 mediate forms really occur in some species ; the forceps of Tro- 

 chobola, for instance, is one of them. We have already noticed 

 above the contrast in the coloring between the two genera ; that 

 of Limnobia being more intense and brilliant, with well-defined 

 stripes, bands, and dots on the body, the wings and the feet. 



2. In the mode of life : Most of the larvas of Dicranomyia 

 are probably aquatic or subaquatic, whereas those of Limnobia 

 live in wood, fungi, etc. 



3. In the venation : The auxiliary vein in Dicranomyia is in 

 most cases shorter ; it usually ends in the first longitudinal vein 

 nearly opposite the origin of the second vein or before it. In 

 exceptional cases only (in four North American species among 

 nineteen), this vein is prolonged a considerable distance beyond 

 the origin of the second longitudinal vein. Just the opposite is 

 the case with Limnobia; the auxiliary vein is, almost without 

 exception, prolonged considerably beyond the origin of the second 

 vein. The only exception I know of is the European L. macro- 

 stigma Schum., the auxiliary vein of which is prolonged only a 

 short distance beyond the origin of the second longitudinal vein. 



