104 



THE PALEONTOLOGICAL DATA 



The key to the solution of the problem was found in the study of the 

 wings of Homaloneura punctata (Fig. 105), from the Upper Upper Carboni- 

 ferous, of Commentry, France. Both wings of this insect are preserved; 



:.• ^2 



Fig. 104. — Stygne Roemeri (After Handlirsch). 



in the front wing media is dichotomously branched and in the hind wing 

 this vein is of the isolated front branch type. From a study of these wings 

 it is evident that the isolated front branch of media of the hind wing is the 

 result of the coalescence of veins Mi and M2 by which a single unbranched 

 vein was formed. 



The beginning of this reduction of vein Mi +2 to an unbranched condi- 

 tion is shown in Metropator (Fig. 97) and in the two species of Paolia (Fig. 

 98 and 99). In each of these the forking of vein Mi +2 is much nearer the 

 margin of the wing than that of vein M3+4. 



Correlated with the reduction of vein Mi +2 to an unbranched condition, 

 there has been in very many of the genera in which this condition exists a 

 moving back of the point of separation of veins Mi +2 and M3+4 towards 

 the base of the wing, which has resulted in an accentuation of the isolation 



of vein M1+2. This is shown to a certain 

 extent in Eurythmopteryx (Fig. 102) and 

 more markedly in Dictyoneura Libellu- 

 loides (Fig. 95). 



In conclusion, the paleontological data 

 indicates that in the primitive insect wing 

 the media was four-branched and the 

 branching was dichotomous. It also 

 indicates that in addition to the four 

 principal branches there was a \'ariable 

 number of accessory veins near the margin 

 of the wing (See foot note page 99). 



The evolution of the cubitus.— A 

 study of recent insects led Comstock and 

 Needham to conclude that in the primitive insect wing cubitus was 

 two-branched; and it is so represented in otn- diagram of the hypothetical 

 primitive type of wing venation. 



Fig. 105. — Homaloneura punctata 

 (After Handlirseh). 



