THE PALEONTOLOGICAL DATA 



91 



families in which there are prothoracic wings.* One of these is repre- 

 sented in Figure 78. 



It is probable that the prothoracic expansions were useful even after the 

 appendages of the second and third thoracic segments became active organs 

 of flight. That they were retained after the loss of the abdominal expan- 

 sions is shown by Lycocercus Goldenbergi, (Handlirsch, PI. X, Fig. 20). 



In all of the remains of the Pal^o- 

 dictyoptera in which both the wings 

 and the body are preserved, the wings 

 are extended. It seems probable, 

 therefore, that they could be moved 

 only vertically. The ability to fold 

 the wings over the abdomen was 

 acquired only by later developed 

 orders. One of the older illustra- 

 tions of this is Spaniodera anibidans 

 (Fig. 79), a member of the Order Pro- 

 torthoptera, found in Illinois and in 

 Pennsylvania, in the Middle Upper 

 Carboniferous. 



Handlirsch believes that the 

 Paleeodictyoptera were amphibious; 

 but it does not seem to me at all 

 probable that this was the case. Two 

 nj^mphs from the Middle Upper Car- 

 boniferous are known : one (Fig. 80) 

 from Sadgley, England; and one 

 (Fig. 81) from Hampton, West Virginia. It is difficult to imagine insects 

 with laterally projecting wing-buds, such as these n\Tnphs possessed, 

 swimming through the water. 



It seems to me obvious that the development of aquatic njTnphs could 

 have occurred only after the developing wings had become folded back 

 along the sides of the body. The fact that the three recent orders with 

 aquatic nymphs, the Odonata, the Ephemerida, and the Plecoptcra, have 

 different types of tracheal gills indicates that they could not have been 

 evolved from a common aquatic progenitor. 



Fig. 79-- 



-Spaniodera ambidans (After 

 Handlirsch). 



(c) ON THE COURSE OF THE EVOLUTION OF EACH OF THE PRINCIPAL 



WING-VEINS 



In otu" efforts to construct a diagram representing the probable tjq^e of 

 the wing-venation of the primitive winged insect Comstock and Needham 



*These are Stenodictya, Lithomantis, Lycocercus, Ilomceophlebia, and Homaloneiirina. 



