30 S. II. SCUDDER ON PALAEOZOIC COCKROACHES. 



Let us now examine the neuration of the wings of cockroaches with special reference to 

 its development, in order to determine which of the two tribes into which we have divided 

 the Palaeoblattariae is to be considered the more primitive type. At the outset we may 

 remark thai were we to base our ideas of the relative rank of the existing suborders 

 of inserts upon the degree of complication of the neuration of their wings alone we should 

 undoubtedly fall into error. Yet, although in studying the most ancient insects this 

 portion of their structure is nearly all Ave have to guide us, we may confidently assume 

 that it is here sufficient to determine their relationship with accuracy. The variation in 

 the structure of the wings of existing insects is the result of a' multitude of forces exerted 

 through aeons, and exhibits every imaginable form from extreme simplicity to excessive 

 complexity : in some insects the wings, like the rest of the body, have retained an ancient 

 simplicity of structure, as in the May-flies; in others they appear to have lapsed into 

 simplicity, or to have retained a simple distribution of the veins, when the other parts of 

 the body have become highly organized, such as the Lepidoptera generally; in still others, 

 by the diversity of use to which the wings have been put, they have become in different 

 ways extremely complicated, so that the plan of neuration is greatly disturbed or nearly 

 lost; as in the hind wings of earwigs, and of many cockroaches and beetles, and in both 

 wings of dragon Hies, —nearly all of which insects are otherwise lowly organized. 



This differentiation of the neuration, we may judge by many proofs, 1 had made slight 

 progress in palaeozoic times. The wings of the then existing insects were comparatively 

 simple and uniform. Nevertheless, the variation of structure was already sufficient in the 

 carboniferous epoch to prove that we must look far back of it for the origin of winged 

 insects. We have already shown that differences existed among cockroaches warranting 

 their division into two great groups; and as a whole this family group was distinctly 

 separated, even at that early time, from all other insects, even as they are to-day, unless 

 we except their nearest allies the Mantidae, in the burial of the innermost anal vein at the 

 bottom of a deep sulcation, dividing the anal area from the rest of the wing. They were 

 also peculiar — although a few ancient types partially shared with them this character- 

 istic — in that the large number of mediastinal branches, as well as the main mediastinal 

 vein, terminate on the costal margin only, and do not leave it simply supported by the main 

 vein lying in close proximity. This peculiarity necessitated a somewhat central origin for 

 the veins at the base of the wing, and apparently led to the diversity noticed in the two 

 types of ancient cockroaches. 



If we were to express in simplest terms the structure of a symmetrically developed wing 

 (like that of the palaeozoic cockroaches with its five principal branching veins), we should 

 figure the middle vein as running straight to the apex, forking as it went and occupying 

 the apical margin with its branches; while the similarly forking branches of the upper two 

 veins would curve toward and terminate upon the costal margin, and those of the lower 

 veins upon the inner margin. A wing has already been found 2 quite as simple in idea as 

 this, but belonging to the other group of palaeozoic insects, in which the wing is not 

 symmetrical, but where all the veins and their branches impinge upon the inner and apical 

 margin of the wing. In such a wing, differentiation of the veins may scarcely be said to 



' Sec the preceding paper: The early types of insects. '-' Scudder. An insect wing of extreme simplicity from the 



coal formation. < Proc. Bost. Soc. Nat., Hist. xix, 248 19. 



