THE WINGS OF INSECTS. 
J. H. COMSTOCK anp J. G. NEEDHAM. 
CHAPTER IV (continued). 
The Specialization of Wings by Addition. 
III. THE VENATION OF THE WINGS OF ODONATA. 
THE wings of dragon flies have furnished the best of system- 
atic characters since the days of Linneus. The many pecul- 
larities of venation have been slowly worked out and expressed 
in a formidable system of terms, most of which designate parts 
bearing other names in other orders. Indeed, this is not strange ; 
Fic. 60.— Wi f hs of Gomphus descriptus, early stages. 
for, from the study of the adult wings alone, the discovery of 
the real homologies would be well-nigh impossible. 
The richly veined wing of a dragon fly, at first sight, shows 
little in common with our hypothetical type. And even when 
the tracheation of the wing of an old nymph is studied, there 
are found some striking discrepancies. But in the budding 
wing of a young nymph we find an arrangement of the trachez 
which is almost that of the typical wing. 
Fig. 60 represents the tracheation of two nymphs of Gomphus 
descriptus. The wing figured at A was only 1 mm. in length. 
Here is a costa with some anterior twigs, a subcosta with a 
terminal fork, a radius with its sector unbranched, a three- 
branched media, a cubitus which is two-branched in the usual 
