PHILIP A. MUNZ 27 



generalized condition. They fall under two or three general heads 

 and may be so treated in their discussion. First come those which 

 may be classified under "Vein Reduction," secondly, those having 

 to do with "Vein Shifting," and as a last group "Miscellaneous 

 Features." 



Vein Reduction 

 I. Reduction in the number of supplementary sectors. — This is one 

 of the most evident means of specialization within any group which 

 possesses such sectors, as well as in the whole suborder, of which 

 the two highest subfamilies have none. A comparison of the dif- 

 ferent subfamilies in this regard may be made in a general way by 

 choosing for each one as its most typical genus the one after which 

 it is named. In Table I this has been done, the figures indicating 

 the number of sectors between the veins listed at the top of the 

 columns. The figures are for the front wings. 



Table I 

 The Number of Supplementary Sectors present in the Sub- 

 families of Zygoptera 



MEM. AM. ENT. SOC, 3, 



