EXPLANATION OE EIGUEES. 



Fig. 1. Wing of a gnat or mosquito {Culex sp.), X about 16. 

 r\ Portion of 2nd longitudinal vein, greatly enlarged, to show 

 the covering of scales : (a) median vein-scales ; (b) lateral. 



P. Portion of hind margin of wing, greatly enlarged, to show 

 the fringe : (a) border-scales ; (b) fringe scales. 

 Fig. 2. The same wing denuded of hairs and scales, to show the 

 course and nomenclature of the veins. 



C. costal vein (in Culicidm this runs right round the 

 margin of the wing) : the anterior margin of the 



wing is called the costa. 



I 



II 



III 



IV 



VI 

 a 

 Tr 

 Tri 

 Tr^ 

 T 





sub-costal vein. 



1st longitudinal vein. 



2nd 



3rd 



4th 



5th 



6th 



wing-folds or pseudo- veins. 



supernumerary cross-vein. 



mid cross-vein. 



posterior cross-vein. 



marginal cross- vein. 

 It will be observed that the 2nd, 4th, and 5th veins are 

 forked (the branch nearer the costa is spoken of as the uppei\ 

 that nearer the hind margin of the wing as the lower branch in 

 each case). The relative lengths of the forks of the 2nd and 

 4th veins vary in different genera and species. 



Fig. 3. Wing of a midge {Chironomius ylumosus^ L.), x about 12, 

 showing that the veins are destitute of scales. 



90 



r" 



