fringed with hair or scales and the costal vein encom- 

 passes the wing ; auxiliary vein distinct, reaching to or 

 beyond the middle of the wing; second, fourth and fifth 

 longitudinal veins furcate; third vein simple, arising 

 from the second angularly beyond the middle of the wing; 

 anterior cross-vein situated near or even proximal of the 

 origin of the third vein. Two basal cells present, elon- 

 gate, the anal cell wide open. Veins of the wings cloth- 

 ed with scales. 



The foregoing description and figure of the wing do 

 not wholly agree with those of other writers. It is evi- 

 dent, unless we change the nomenclature of the brachy- 

 cerous flies, that the furcation of the second vein does 

 not form a submarginal cell; the so-called 'first submar- 

 ginal cell' is in reality the second marginal. Further- 

 more, it is as clearly apparent that the so-called 'poste- 

 rior cross-vein' is not the vein of that name among the 

 brachycerous and cyclorrhaphous flies, but is, rather, the 

 'discal' or 'discoidal cross- vein', or the 'anterior basal 

 cross-vein'; or, at least, a cross-vein which has not yet 

 received a definite name. 



Since the last edition of this work was published, in 

 1896, the marvelous discoveries in the life histories of the 

 Culicidse, and their agency in the transfer of disease, 

 have given to the family an importance in man's econo- 

 my second to that of no other group of insects. Indeed, 

 one may say with entire truth that these little flies, or 

 'gnats' as the English call them, are the most baneful 

 and pestilential of all known insects. The microscopical 

 parasites producing malaria, yellow fever and filariasis 

 are now 7 known with certainty to be transferred by the 

 agency of certain mosquitoes from one human being to 

 another, and it is probable, though of course not certain, 

 that if all the germ-bearing mosquitoes could be made 

 extinct these diseases would at least cease to trouble 



