2 A VENATIONAL STUDY OF THE ZYGOPTERA 



III. Tendencies in Specialization 26 



Vein Reduction ~1 



1. Reduction in the number of supplementan' sectors 27 



2. Reduction of the veins Cu^ and Cui . 28 



3. Decrease in the number of antenodal cross-veins 28 



4. Decrease in the number of postnodals 29 



5. Loss of the cross-veins in the quadrangle and subquadrangle 29 



6. Reduction in the number of those antenodal cells situated between M4 

 andCui 29 



7. Reduction in the number of cross-veins behind the anal vein 29 



Vein Shifting 3^ 



1 . Narrowing of the wing 30 



2. Progressive petiolation 3^ 



3. Retraction of the nodus toward the base of the wing 31 



4. Tendency Jor M2, Rg, and M3 to arise nearer the tip of the wing and 

 further from the subnodus 31 



5. Migration outward of the base of Mia 33 



6. The position of the second antenodals before the arculus 33 



7. The tendency for the quadrangle to become acute distally 33 



8. Change in the length of the quadrangle 35 



9. Attachment of supplementary sectors 35 



10. Straightening of the longitudinal veins 35 



1 1 . Matching up of the cross-veins in trans\erse series 36 



Miscellaneous Features 36 



1. Differentiation of fore and hind wings 36 



2. The bracing of the stigma 3^ 



3. Atrophy of the stigma 37 



IV. Summary 37 



V. Keys for the Identification of Genera 38 



The Anisozygoptera 40 



The Zygoptera 4^ 



"The Agrionidae 40 



The Polythorinae 42 



The Agrioninae 42 



■ The EpaUaginae 45 



The Disparocyphinae 47 



The Coenagrionidae 4^ 



The Lestinae 4^ 



The Lestoidinae 49 



The Pseudostigmatinae 49 



The Megapodagrioninae 5t> 



The Coenagrioninae 53 



The Proloneurinae 63 



VT . Bibliography 67 



VII. Plates 72 



