Vol. 1.] 



Woodworth. — Wing Veins of Insects. 



113 



The wings are quite free from cross veins. The character of 

 the venation is shown in Fig 51. 



The remaining Paleozoic Orthopteroidea exhibit a general 

 resemblance to the in- 



sects just considered, 

 but are distinctly more 

 like other insects of the 

 time. Cross veins are 

 always present. The 

 longitudinal veins are 

 proportionately very 

 much smaller in diam- 

 eter and not so strictly parallel, bvit they nevertheless resemble 

 the Palaeoblattidse more nearly than do any other insects. 



FIG. 51. Diagram of the venation of the Palaso- 

 blattidse. The figures indicate tlie range of 

 variations in tlie number of veins in each area. 



ELYTROPTERA. 



This group is unquestionably unnatural from a systematic 

 point of view, since there are no grounds for supposing that 

 there is any close relationship between either of the orders 

 here assembled. Each order has responded in much the same 

 way to the requirements of a similar environment, and so 

 they present many characters in common. The name here 

 proposed (Elytroptera) is therefore simply one of convenience. 



The anterior wings show a tendency toward the suppression 

 of the venation, owing to the membrane becoming throughout 

 vein-like in texture, so that the whole surface is more nearly 

 uniform. The posterior wings come to exceed in size the 

 anterior, and so are folded enough to be covered by them, the 

 venation becoming involved in the folding mechanism. In 

 this group, therefore, the study of the folding and its influence 

 on venation is of paramount importance. 



BLATTID^E. 



The specialization of the Blattida^ from the Pala?oblattidae 

 consists in the thickening of the front wings, the perfection 

 of the posterior region of the hind wings, and the changes 

 incident to folding. The effect of the former process is rather 

 the suppression of venation when carried to the extreme, and 

 need not be considered in detail. 

 8-v 



