THE WINGS OF ODONATA 



235 



The fifth named supplement is the cubital supplement. This is described 

 later; it is found in the cubito-anal loop of the Libellulidse. 



The manner of development of a supplement is illustrated by Plate 

 VIII, Fig. I which represents a part of the wing of a grown nymph of Anax 

 Junius. The principal trachea shown is the radial sector trachea, whose 

 branches extend into intercalary veins; the strong developing vein that 

 sets across them, bending toward the radial sector trachea at both ends, is 

 the radial supplement (rspl). It will be seen to be a purely cuticular vein, 

 without trachea of its own (Needham '03). In Fig. 2 of the same plate, 

 both the radial and the median supplements are shown. 



The antenodal cross-veins. — Much use is made in taxonomic work of the 

 two series of cross-veins that are nearest the costal margin of the wing. 

 Those of these cross-veins that are situated between the base of the wing 

 and the nodus are termed the antenodal cross-veins (Fig. 230, an). The 

 first of these two series of antenodal cross-veins extend from the costa to the 

 subcosta; the second, from the subcosta to the radius. The antenodal 

 cross-veins are termed the antecuhital cross-veins by some writers. 



"Specialization is to be traced among these cross-veins in their reduction 

 in number and matching in position in the two series, and in the hyper- 



Wings of Boyeria Irene. 



trophy of some of them to form stout triangular trusses, which entirely fill, 

 in section, the fuiTow between the costa and radius. Two antenodals, some 

 distance apart, are thus hypertrophied in most Aeschnida, one at either 

 side of the arculus; in the Thorinae, but one, and that one meeting the 

 arculus; in Synthemis, alternate antenodals are thickened, but to a less 

 degree." (Needham '03). 



