190 DIPTERA OP NORTH AMERICA. [PARI IV. 



Section IV. LIMNOPHILINA. 



Two submarginal cells ; usually five, seldom four posterior cells ; discal 

 cell generally present ; subcostal cross-vein posterior to the origin of the 

 second longitudinal vein, usually closely approximated to the tip of the 

 auxiliary vein (considerably distant from it in Trichocera only). Eyes 

 glabrous (pubescent in Trichocera). Normal number of antennal joints 

 sixteen. 1 Tibiae with spurs at the tip ; empodia distinct ; ungues smooth. 



The contrast between the characters of the two sections of 

 Limnophilina and Limnobina, has been explained under the 

 head of the latter. This contrast shows itself, moreover, in 

 another manner : While " the forms of Limnobina, belonging 

 to the temperate regions of Europe and America, afford but little 

 structural diversity, and their relationship is so great and evident 

 that one is more tempted to unite them all in one genus, than to 

 subdivide them in several" (compare above, p. 51), precisely the 

 contrary is the case with the species of Limnophilina. The struc- 

 tural modifications they show are so numerous, that the desire to 

 introduce new generic groups is restrained by the fear of adopting 

 too many. At present, the section Limnophilina consists, properly 

 speaking, of the single genus Limnophila ; Trichocera is an 

 aberrant form, singular in its structure as in its mode of life. 

 Epiphragma and Ulomorpha are Limnophilse, but sufficiently 

 well-defined forms to be separated immediately, as several other 

 forms will have to be separated, when better known (compare the 

 genus Limnophila below). 



The difference between the Limnophilina and Eriopterina, 

 besides the presence of spurs at the tip of the tibiae, consists in 

 the following characters : The subcostal cross-vein in the majority 



1 This refers to the European and North American species ; Gynoplistia 

 Westw. has ($) 18-, and (£) 17-jointed antennae; Ctedonia Phil, has 

 15-24 joints, etc. 



