242 



THE WINGS OF ODONATA 



believed to represent the connecting link between the Palasodictyoptera and 

 the Odonata, and in which there was an even greater number of intercalary- 

 veins developed than exists in the Odonata. 



The characteristics enumerated above exist in all wings of the Odonata 

 known excepting one. In Diastatonima Hasina (Fig. 231), which was found 

 in the Lower Lias in England, there is neither a nodus nor a secondary- 

 anal vein. This is one of the oldest of the Odonata known, and may be 

 regarded as the nearest approach to the stem form of the Odonata yet dis- 

 covered. The presence in this wing of a well-developed intercalary vein in 

 area Mi (Fig. 231, IMi) indicates that the perfection of the alternation of 

 convex and concave veins had already been attained. 



Passing from the consideration of those specializations that distinguish 

 the order Odonata as a whole to those that mark its subdivisions, we come 

 into a field that can be adequately treated only by those having a very 

 extended knowledge of the order, a field that the writer will not presume to 

 enter. A notable contribution to it has been made by Professor Needham 

 in his "A Genealogic Study of Dragon-fly Wing-Venation" ('03). As 

 anyone working in this field will need to consult this fundamental paper, I 

 will not take the space to abstract it here. 



(d) COMPARISON OF TERMINOLOGIES OF THE WING-VEINS OF THE ODONATA 



