THE WINGS 6] 
transverse portion has been frequently called the “ supernumerary cross-vein.” 
The fourth, fifth and sixth veins arise at the base of the wing. A small cross 
vein, which joins the basal part of the third vein with the fourth vein, is 
called the anterior cross-vein. Another cross-vein joins the fourth vein anc 
the upper branch of the fifth vein and is called the posterior cross-vein. The 
osterior cross-vein is usually a short distance behind the anterior cross-vein, it 
Hay, however, be in line with it or even beyond it. There is also a humeral 
cross-vein, close to the base of the wing between the costa and the auxiliary vein. 
Between the first and auxiliary veins and behind the origin of the second vein 
is the subcostal cross-vein. Besides these veins there are chitinizations resem- 
bling veins and sometimes in continuation of them. These ‘are variously de- 
veloped in the different forms. The second and third veins are usually thus con- 
tinued longitudinally backward from the point of angulation. A particularly 
heavy chitinization follows the fifth vein on the anal side, and in Megarhinus, 
costal cell é petiole oy 24 inarginal cell 
humeral crossyein t auxiliary vein)! ce 
v costal vein _/ $ H ~submarginakeelt: 
= a Z ‘ H —————— — 
SSS) [ fs SS 
re, Se — ee marginal: cell ; ae f 
- 2d marginal cell 2 
Sub . aoe 
. ") Marginal cell =| 2 
3 
Fig. 3.—Venation of wing of Culea. 
where the chitinizations are particularly marked, there is also a chitinization in 
front of the lower branch of this vein. In some forms there is a chitinization, 
usually poorly defined, which traverses the hindmost area of the wing (the 
axillary cell) longitudinally and forms a more or less well-marked fold. In 
Megarhinus it is particularly distinct. In the case of certain African mosqui- 
toes this fold bears a few scales. It has been incorrectly looked upon by Theobald 
as a seventh vein and upon this character he founded a subfamily, the Hepta- 
phlebomyine. 
The relative length of the fork and the stem, particularly in the second vein, 
is in some cases of diagnostic value, not only specifically but generically. Thus 
the genera Megarhinus and Uranotenia are remarkable for the very short 
branches of the second vein. The part of the wing enclosed by the two branches 
of the second vein is the second marginal cell ; it is often incorrectly called the 
first submarginal cell. The position of the posterior cross-vein in relation to 
the anterior cross-vein is also of significance in classificaton, although there is 
naturally some individual variation. 
The wings are clothed with scales along the veins and along their margins. 
These scales show great diversity in shape and characters in different species and 
