230 



numerous small spinules and, laterally, 2 or more small tubercles ; legs 

 extending well beyond apices of wings, apices of fore tarsi extending 

 beyond apices of mid pair, apices of hind pair extending beyond apices 

 of fore pair. Abdomen without noticeable armature; apical segment 

 of female elongate, the upper processes longer than the lower, that of 

 male obtuse, with 7 slight protuberances, 3 in a transverse line be- 

 fore apex on dorsum and 4 at apex — 2 above and 2 below, the latter 

 acute. 



The material used in drawing up the foregoing descriptions is that 

 which Mr. Hart had when he wrote his paper on Illinois River species. 

 He did not describe the early stages, referring merely to Beling's de- 

 scription of them which appeared in a European publication. 



Gnophomyia Osten Sacken 



GENERIC CHARACTERS 



Larva. — Head rather small, wholly retractile, posteriorly com- 

 posed of slender chitinized rods. Body covered with dense silky 

 hairs. General form similar to that of Helobid, the principal differ- 

 ences being the much less conspicuous hairs on the surface of the lat- 

 ter, the absence of distinct ventral locomotor organs, and the longer 

 radiating processes of the apical segment. 



Pupa. — The structure of the thoracic respiratory organs suffi- 

 ciently distinguishes this genus from Helobia. 



HABITS OF LARVAE 



The larvae live in mud, especially along the banks of streams. 



HABITS OF IMAGINES 



The flies are usually found in damp situations, especially in grass 

 along the margins of ponds or streams. They feed on nectar or liquids. 



Gnophomyia tristissima Osten Sacken 



Gnophomyia trisiissima Osten Sacken, Proc. Acad. Nat. Sci. Phila., 1859, p. 224. 



Larva. — Length, 9-1 1 mm. Slender, slightly tapering towards 

 both extremities, more decidedly towards the cephalic. Body yellow- 

 ish testaceous, covered with dense decumbent pile. 



Head more compact than that of Helobia, the lateral rods stouter 

 (PI. XXXIV, Fig. 10); antennae very small; maxillae large, pro- 



