WING VENATION 



17 



tively alternate as convex and concave veins, a feature previously 

 noted by Adolph in 1879. He also claimed that the oldest insects 

 exhibit the richest venation, which disappeared to a marked extent, 

 among recent forms, by reduction. Subsequent researches by 

 him in conjunction with Brauer, and also by Spuler, considerably 

 extended what little had been previously known of the relations 

 of venation to the antecedent tracheation. It was not, however, 

 until 1898 that any comprehensive ontogenetic studies were 

 undertaken. In that year Comstock and Needham began their 

 investigations of the homologies and development of the wing 

 veins in all orders of insects and, in 1918, Comstock extended and 



Fig. 7. Hypothetical scheme of wing venation according to Comstock 

 and Needham. C, costa ; Sc, sub-costa ; R, radius ; Rs, radial 

 sector ; M, media ; Cu, cubitus ; lA, 2 A, 3 A, anals. 



consolidated this work in his well-known text-book on the subject. 

 It may be said, very briefly, that, in the Comstock-Needham 

 system, the original vein nomenclature of Redtenbacher is followed, 

 but with many modifications with regard to his theoretical 

 deductions. By means of an extensive study of the tracheae 

 which precede and, in a general sense, determine the courses of 

 the veins, these authors came to the conclusion that existing types 

 of venation (living and fossil) are all derivable from a common 

 hypothetical ancestor, and that the veins in different orders of 

 insects can consequently be homologised with one another. They 

 further concluded that deviations from the hypothetical ancestral 

 type resulted, either by the addition or by the reduction of veins, 

 as the case may be. No great importance was attached to 

 Redtenbacher 's theory that convex and concave veins alternate 



