Vol. 1.] Woodworth. — Wing Veins of Insects. 143 



RESUME AND CONCLUDING REMARKS. 



The purpose of the foregoing study has been to establish a 

 rational theory of venation. The development of this theory 

 has involved numerous radical departures from the views 

 usually held, not only in regard to the venation itself, but also 

 to the origin of the wing and its effect on the evolution of the 

 thorax. I believe there have been ample grounds for the 

 changes that have been proposed, and all that fit together to 

 make a comprehensive general scheme whereby the nature of 

 venation as a whole, and a host of peculiarities in individual 

 venations before unexplainable, are made clear. 



The wings are conceived of as organs whose function is so 

 definite, and the requirements of which are so exacting, that 

 the mechanical necessities are the dominant factors in their 

 first production and in all subsequent specializations. Thus, 

 in the origin of the wing the most important matter was its 

 utility for flight. It was this that was responsible for the 

 location of the wings on a particular region of the insect's 

 body, even for the determination of the part of the segment 

 occupied. A wing could not have been produced in another 

 situation, since flight is dependent upon equilibrium. The 

 shape and structure of the organ are determined by its func- 

 tion, to a predominating extent. There must be a wide, 

 expanded area, coupled with lightness and strength, and the 

 latter must be distributed so as to meet the particular strains 

 to which the wing is to be subjected. The relation to the body 

 must be such as to permit the proper motion of the wing, even 

 though it require the readjustment of the whole thoracic 

 structure — indeed, it is clearly responsible for the most profound 

 change in the structure of the body wall that the segments 

 have experienced. It could also be shown that the internal 

 structures were subjected to a similar readjustment. 



In the wing itself, the one specialization of importance for 

 aerial locomotion is the production of the veins. These struc- 

 tures are developed primarily for strength. Any other function 

 is certainly secondary. Their structure when best developed 



