84 MEMOIES OF THE XATIOifAL ACADEMY OF SCIENCES. 



IX.— A RATIONAL NOMENCLATURE OF THE VEINS OF INSECTS, ESPECIALLY THOSE OF LEPIDOPTERA. 



Hitherto there has been an unfortunate lack of uniformity in the nomenclature of the veins 

 of the wings, different names having been applied to the veins of different orders of insects. 



In his jiaper on the phylogeny and ontogeny of the veins of the wings of Lepidoptera, Spnler 

 has, however, given us a simple scheme and a numbering of the veins which will, we think, apply 

 in general to the wings of insects of all orders. 



Eedtenbacher had previously pninted out that "the geologically older Orthoptera and 

 Neuroptera have a much richer and more com[)licated venation than the Coleoptera, Lepidoptera, 

 Hymenoptera, aud Dijitera; thus among the Rhynchota the oldest forms, the Cicadidse and 

 Fulgorida-, have a much greater number of veins than the Hemiptera. There is no doubt but 

 that the oldest insects were provided with an excess of veins; that, on the other hand, in the course 

 of development this superfluity has disappeared by a process of reduction, and in this way a simpler 

 system of venation has resulted. It is also to be observed that the size f)f the wings has had a 

 considerable influence on the number of the veins, since small forms almost without exception 

 have fewer veins than insects with large wings." Eedtenbacher also believes "that the normal 

 type of a differentiated wing may be found in those insects whose fore and hind wings are most 

 similar in size aud shai)e," and states that the venation is not useful as an ordinal character, but 

 is of more service in separating suborders and families. 



We agree with Spuler in rejecting Redtenbacher's system, which is partly based on Adolph's 

 lantenable theory of convex and concave veins, but more especially for the reason that 

 Eedtenbacher assumes that the primitive form of venation is that of the Ephemerida\ He 

 remarks: "There is scarcely another group of insects whose wings show the primitive type, the 

 fan-shaped form, as the May flies." It may be objected to this that the Ephemerid*, though in 

 most respects generalized and primitive insects, yet are, as regards the wings, highly modified or 

 sjiecialized. That this is the case is also suggested by the reduction or atrophy of the mouth 

 parts. On the other hand, the retention of sexual organs paired throughout, the ducts remaining 

 separate, with open, paired outlets, shows that the May flies are, in this respect, more primitive 

 than any other winged insects. But as regards the thorax and the wings, we observe that in 

 them a high degree of modification has taken i)lace. Thus the two pairs of wings are very unlike 

 in size and shape, and this feature is a secondary one. Hence the large number of main 

 longitudinal veins in the wings of Ephemera is a case of irrelative repetition of parts mostly 

 situated in the fau-like field, due to a jirocess of specialization, a process which is manifested in 

 quite another way in the wings of the Dermaptera, also a primitive type. 



Redtenbacher regards the eleven longitudinal veins (I-XI) of Ephemerids as the normal 

 number, and considers that the Trlchoptera, Lepidoptera, etc., have lost certain of the veins by a 

 process of reduction. This view has beeu adopted by Comstock in his suggestive paper, 

 " Evolution and taxonomy," but it seems to us to be untenable, the anal field ("faltentheil" of 

 Spuler) not being of primary importance. On the other hand, Redtenbacher's use of Eonian 

 numerals for the main veins, and of a combination of Eoman and Arabic numerals for their 

 branches, is very convenient. 



Spuler divides the wings of each pair into an outspread portion [Spreitentheil) and a folded 

 part [Faltentheil). The A'eins of the former area he numbers in the same manner as Redtenbacher, 

 beginning on the costal edge of the wing, while those of the folded area (the subnjediau and 

 internal or first and second anal veins of other authors) he does not name, but simply numbers 

 with the Greek letters a fi. He considers that Hagen was right in believing the Phryganida', 

 TipulariiB, and some Microlepidoptera to be forms with a schematic, i. e., primitive venation 

 (Stettin. Ent. Zeit., p. .SIC, 1870). 



Spuler shares the opinion of Fritz Miiller (Termitida?), Brauer and Eedtenbacher (Libellulidre), 

 and Haase (Papilionida'), that the costa is only a hypodermal structure, a thickening of the edge, 

 which does not have a trachea as its origin (Anlage), and which therefore has nothing to do with 

 the veins. 



