304 The Two-winged Flies 



Of this section the mosquitoes, black flies, and punkies are perhaps best 

 known because of the annoyance and irritation caused by their "bites," 

 that is, the punctures made by the sharp beak of the females in their blood- 

 sucking forays. But the swarms of dancing midges and the sprawling long- 

 legged crane-flies, or leather-jackets, are not unfamiliar members of this group. 

 In addition there belong here a few families of flies little known but possessed 

 of most interesting habits and form. 



KEY TO FAMILIES OF NEMATOCER.\. 



(The references to the names and charactT of the veins in the wings which occur in 

 this and other keys used in this chapter may be understood by a comparison of the 

 venation of the specimen being examined with Fig. 18, and with the figures of the 

 venation of various families, as Figs. 425, 436, 444, etc.) 



A. .^ntenns slender, longer than thora.\; usually nearly as long as body or longer; 

 legs long and slender, and abdomen usually so. 



B. Ver\' small moth-like flies, with body and wings hairy; wings with g-ii longi- 

 tudinal veins, but no cross-veins except sometimes near the base of the wing. 



(Moth-like flics.) PSYCHODID^. 

 BB. Xot as above. 



C. Wings with a network of fine vein-like lines near the outer and hinder 



margins in addition to the regular (heavier) venation. 



(Net-winged midges.") BLEPHAROCERlDi. 

 CC. The margin of the wings and the veins fringed with scales. 



(Mosquitoes.) CnLlciDi. 

 CCC. With a distinct V-shaped suture on the back of the thorax. 



(Crane-flies.) TlpmiDi. 

 CCCC. Without distinct V-shaped suture on the back of the thorax. 



D. .Anal veins entirely wanting; medial vein wanting or at most 

 represented by a single unbranched fold. 



(Gall-gnats.) CEClDOiryilD.c. 



DD. .Anal veins present or represented by folds; medial vein present 



or at least represented by a fold which is usually branched. 



E. Ocelli present; kjs slender and with greatly elongate 



cc.N.-E (basal segment).. .(Fungus-gnats.) Mvcetophilid.e. 



EE. Ocelli absent. 



F. Wing-veins well developed in all parts of the wing. 



(Di.xa-flies.) DixiD.€. 

 FF. Wing-veins much stouter near the costal (front) 

 margin of the wing than elsewhere. 



(Midges.) Chironomid.e. 

 AA. Antennje shorter than the thorax and rather stout. 



B. Ocelli present (March-flies.) Bibiosid.e. 



BB. Ocelli absent; wings very broad (Buffalo-gnats.) SisrCLiiD.E. 



Of the ten families included in the above key the members of five pass 

 the young stages, larval and pupal, in fresh water; of the members of two 



