THE WINGS OF IIYMENOPTERA 



373 



the fore wings ; in the hind wings, the reduction of the venation is greater 

 than this in all cases. The hind wing of Pamphilius (Fig. 39 1 ) is an example 

 of the most generalized condition found in the hind wings of Hymenoptera. 

 While the reduction of the venation of the fore wings is slight in the 

 more generalized members of the order, it is extreme in the more specialized 



Fig. 393. — Wing of an ichneumon-fly. 



families, as in the Chalcidid^e, where frequently only a vestige of the wing- 

 venation remains. 



In the Hymenoptera, as in other orders where the specialization of the 

 wing-venation is by reduction, the lessening of the number of wing-veins is 

 the result partly of the atrophy of veins and partly of the coalescence of 

 adjacent veins. 



The beginning of the atrophy of a vein is illustrated by the subcosta of 

 the hind wing of Pamphilms (Fig. 391), the basal part of which has faded 

 out. In the hind wing of Macroxyela (Fig. 392) the atrophy of the subcosta 

 is complete. In the fore wing of Paniphilins vein Ro has been lost; and in 

 the fore wing of Macroxyela vein Cu2 is lacking. A comparison of these two 

 wings makes evident the fact that in each case a vein has atrophied. 



rsl A 

 Fig. 394.^\Ving of a braconid. 



In Phamphilius no vestige of the lost vein Ro remains. In Macroxyela 

 a bend in the cubitus indicates the position of the fonner forking of this 

 vein. In many other cases, however, vestiges of lost veins remain either as 

 short spurs or as faint lines. 



