THE PALEONTOLOGICAL DATA 



105 



The two-branched condition of cubitus is clearly shown in the Plecop- 

 tera (Fig. 12), Corrodentia (Fig. 4), Odonata (Fig. 228), Homoptera (Fig. 

 270), Trichoptera (Fig. 320), Lepidoptera (Fig. 344), Diptera (Fig. 357), 

 and Hj-menoptera (Fig. 391). 



In the Orthoptera and in the Neuroptera we found that frequently there 

 are on one or both of the two principal branches of cubitus a variable num- 

 ber of accessory veins; but we found no constancy in the number or in the 

 position of these accessor}^ veins, closely allied genera showing marked 

 differences in these respects. We felt, therefore, that the stem fonn from 

 which the recent orders of insects have been evolved had, without doubt a 

 two-branched cubitus. 



When we turn to the study of the Paleozoic insects we find a much 

 smaller amount of data regarding the form of cubitus than we found 

 regarding either of the veins already discussed. This is due to the fact 



Fig. 106. — Paolia vetusta (After Handlirsch). 



that frequently in otherwise well-preserved wings the cubital and anal 

 areas are lacking entirely or in part ; this is especially true of the basal parts 

 of the cubitus and the anal veins. 



In four of the eight wings found in the Lower Upper Carboniferous the 

 cubitus is fairly well-preserved. We will begin our study of the paleonto- 

 logical data with these, the oldest known insect remains. 



In Paolia vetusta (Fig. 106) the cubitus has two principal branches each 

 of which bears accessory veins near the margin of the wing. These acces- 

 sory veins are branched very irregularly. So irregular is this branching, 

 that it does not seem probable that it was even of specific value ; evidently 

 a definite arrangement of the accessory veins borne by cubitus had not 

 yet been attained; and we can regard only the main stem and the two 

 principal branches as being fundamental. 



In Stygne Roemeri (Fig. 107) we find a more advanced stage of specializa- 

 tion; this is evident from the fact that definite cross-veins had been 

 attained, which is not the case in Paolia. In Stygne each of the two princi- 

 pal branches of cubitus bears several branches; the cubital area being 

 greatly widened at the margin of the wing, and well-supplied with accessory 

 veins, most of which have attained a definite longitudinal direction. 



