90 G. R. Osten Sacken: Diptera 



body) and slender; tiljiae without spurs; ungues minute, empodia not per- 

 ceptible; wings about as long as the abdomen; venation as explained above. 



There is another species still, whicb very probably belongs here; 

 it is ihe Cylindrotoma albitarsis Dolesch. 2 Bijdr. 15, Tab. IV, f. 1 

 from Java. The likeness of the venation between Dr. Doleschall's and 

 Prof. Westwood's figures is obvious, and consists principally in the 

 immediate contact of the submarginal with the discall cell, involving 

 the absence of the small crossvein, and in the presence of the two 

 crossveins *) inside of the marginal cell, The difference between them 

 is, that in Doleschall's figure there is one cell less; and assuming that 

 this figure is correct, we may express this difference by saying, that 

 in Mr. Westwoods figure there are four posterior cells, in Doleschall's 

 only three; or, should we adopt a diflFerent Interpretation of the veins, 

 that in Doleschall's figure the submarginal cell is wanting. Both 

 alternatives represent a form of venation which is of very rare occurence 

 among diptera, and we must suspend our judgment on this point, until 

 we have an opportunity of seeing the insect from Java, described by 

 Doleschall. But in the mean time, the presence, in the three species 

 of the extraordinary crossveins in the marginal cell, the unusual length 

 and slenderness of the legs common to them, and indicative of the 

 habit of aerial dancing, (attributed by Doleschall to his O. albitarsis), 

 the white tarsi, also common to the three species, all these characters 

 tend to establish a very strong presumption in favor of their generic 

 identity. ^) 



A fourth species, which may claim a relationship with the other 

 three, is the Limnobia Trentepohlii Wied. I, 551; Tab. VI, b, fig. 12 

 (Sumatra). Here, the analogy with Doleschall's figure is very striking: 

 the long oblique crossveins in the marginal cell, only three posterior 

 cells, and a very abruptly curved fifth vein; but the discal cell is open; 

 about the structure of the species too little is said to allow any conclusion. 



The Position of Mongoma in the system is somewhat doubtful. 

 A Tipülid with 16-jointed antennae and without empodia and spurs, 

 must be placed provisionally among the himnobina anomala. Para- 



^) I call them crossveins merely for shortness sake, because one 

 of them may also be considered as a brauch of the second vein. 



•) Doleschall is probably wrong when he calls the antennae of 

 his C albitarsis 14-jointed; in the same way he counted 16 joints on 

 the antenna oi Dicranomyia saltans, which has only 14; and 16 joints 

 on that of his Cylindrotoma ornatissima, while his own drawing, a copy 

 of which I possess, shows 22 joints, that number being certainly much 

 nearer the truth than the other. 



