86 DIPTERA OP NORTH AMERICA. [PART IV. 



feet, and spots on the wings ; they form, in this respect, a contrast 

 with the usually dull coloring of the Dicranomyise. 



The last antennal joint of this genus often shows a cylindrical 

 prolongation, sometimes slightly clavate at the tip, which, even 

 in living specimens, looks like a fifteenth joint. That this is not 

 a real joint seems to be proved by the circumstance that closely 

 allied species differ with regard to its structure ; one species may 

 appear to have 15-jointed antennae, whereas in the next one only 

 14 joints can be counted. 



The larvae of this genus live in decaying vegetable matter, 

 especially in wood and fungi. Stannius {Beitrage, etc. p. 202) 

 found the larva of Limnobia xanthoptera (a species related to 

 the North American L. triocellata) in an Agaricus ; the larva 

 was wrapped in a sheath of earthy matter, rough on the outside, 

 smooth and shiny on the inside ; it went underground for trans- 

 formation. Yan Roser (Verz. Wicrt. Dipt.) discovered the larvae 

 of L. annulus (closely allied to L. cinctipes Say) in decayed 

 wood ; they are like an earth-worm in size, as well as in color, 

 and line their burrows with a kind of silken web. 



Limnobia may be subdivided in two groups, defined by the 

 position of the marginal cross- vein. 



The first group, having the cross-vein close by the tip of the 

 first longitudinal vein, contains large, very characteristic species, 

 the typical Limnobise. A remarkable parallelism exists in this 

 group, between the species from Europe and from North America. 

 L. annulus Lin. is closely allied to L. cinctipes Say; L. quadri- 

 notata Meig. is analogous to L. solitaria; and L. xanthoptera, 

 although belonging to a somewhat different type, is represented 

 in North America by L. triocellata. 



In the second group, the marginal cross-vein is at some 

 listance from the end of the first longitudinal vein, and more or 

 less approximated to the middle of the stigma. The ovipositor 

 of the females of this group is more long, slender and pointed 

 than the ovipositor in the first group ; the short, curved shape of 

 the latter being more like the ovipositor of Dicranomyia. Four 

 North American species belong to this group, two of which have 

 clouded, and the two others almost immaculate wings. In Europe, 

 this group is more abundantly represented, and there is a number 

 of handsome species with more or less pictured and clouded wings, 

 which, as far as known, have no representatives in North America 



