DICBANOMTIA. 367 



case the auxiliary vein ends in the 1st longitudinal and not in the 

 costa as usual.* 



In Dicranomyia the marginal cross-vein is always at the tip of 

 the 1st longitudinal, and generally in a straight line with it. 

 In Limnobia it is often some distance before the tip, occurring in 

 the middle of the stigma or even at its basal end, and when this 

 occurs it is generally in the less typical species of the genus. 

 In typical Dicranomyia the marginal cross-vein is close to the tip 

 of the 1st longitudinal vein. 



The discal cell is often open (adventitiously or as a specific 

 character) in Dicranomyia, but hardly ever so in Limnobia. 

 A difference between these two genera is also noticeable in the 

 larval stages, as the larvae of Dicranomyia are aquatic or sub- 

 aquatic, whereas at least some species of Limnobia are known to 

 breed in wood and fuugi. 



Differential characters of minor importance may be found in 

 the general facies, in Dicranomyia the legs being comparatively 

 longer and more slender, in Limnobia generally shorter and 

 stouter ; further, the coloration of the present genus is generally 

 sombre, grey, blackish, and brownish, whereas in Limnobia there 

 are numerous brightly coloured yellow and orange species, with 

 conspicuous black marks, often on the wings as well as on the 

 bodies. Some species of Dicranomyia have delicately marked 

 wings. 



Life-history. The larva is aquatic or subaquatic, some of the 

 species apparently preferring running water. Osten Sacken 

 found the larva of one species (probablv D. defuncta, Os. Sac., 

 which, according to Aldrich, =simulans, Walk.) on the woodwork 

 ot a mill-dam, with a stream of water constantly passing over it ; 

 in fact, that author frequently saw the flies themselves alight on 

 stones and rocks over which a very thin sheet of water was running. 



Winnertz records rearing the Pala3arctic species D. dumetorum, 

 Mg., from decaying beech-stumps (Linn. Entom. viii, p. 281). 



The perfect insects are found in woods, especially near streams 

 and small trickling miniature water-falls. They not infrequently 

 occur in houses, often attracted by an artificial light at night. 



Table of Species. 



1. Ground-colour of wing marniorated by the 



presence of numerous very small pale grey 

 spots, in addition to darker and more con- 

 spicuous markings 2. 



Ground-colour of wing never marmorated . 3. 



2. Legs pale yellow ; tips of femora, especially 



fore pair, widely black ; wings pale grey, 



with darker small spots, no larger spots [p. 369. 



on costa marmoripennis, sp. n., 



* Osten Sacken notes that this latter peculiarity, viz., the subcostal cross- 

 vein being situated so as to unite the auxiliary vein and the costa, was not 

 known to him to exist in any other genera of TIPULID.E. 



