EXPLANATION OF FIGURES. 
Fig. 1. Wing of a gnat or mosquito (C'ulex sp.), x about 16. 
l a . Portion of 2nd longitudinal vein, greatly enlarged, to show 
the covering of scales : (a) median vein-scales ; (b) lateral. 
l b . 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 Culicidw this runs right round the 
margin of the wing) : the anterior margin of the 
wing is called the costa. 
I a , sub-costal vein. 
I, 1st longitudinal vein. 
II, 2nd „ 
III, 3rd 
IV, 4th 
V, 5th 
YI, 6th 
a, wing-folds or pseudo- veins. 
Tr, supernumerary cross-vein. 
Tr 1 , mid cross-vein. 
Tr 2 , posterior cross-vein. 
Tr 3 , marginal cross-vein. 
It will be observed that the 2nd, 4th, and 5th veins are 
forked (the branch nearer the costa is spokeu of as the upper, 
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 (Chironomus plumosus, L.), x about 12, 
showing that the veins are destitute of scales. 
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