84 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



IX.— A RATIONAL XOMEXCLATLRE OF THE VEINS 01" INSECTS, ESPECIALLY THOSE OF LEPIDOPTERA. 



Hitherto there lias been au unfortunate lack of uniformity in the nomenclature of the veins 

 of the wings, dift'ereut names having- been applied to the veins of difl'ereut orders of insects. 



In his paper on the pliylogeny and ontogeny of the veins of the wings of Lepidojjfera, Spnler 

 Las, 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. 



Kedtenbacher hud previously p )inted out that '-the geologically older Orthoptera and 

 Neuroptera have a much richer and moi-e complicated venation than the C(jlei)ptera, Lepidoptera, 

 Hymenoptera, and Diptera; thus a;uong the Ithyuchota the oldest forms, the Cicadida- aud 

 Eulgoridic, have a much greater number of veins than tlu^ Ilemipteia. There is no doubt Jbi'.t 

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

 of development tiiis superfluity has disappeared by a process of reduction, aud iu this way a simpler 

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

 considerable iuduence on the luimber of the veins, since small forms almost without excei)tiou 

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

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

 similar in size and shai)e," and states that the venation is uot useful as an ordinal character, but 

 is of more service in separating suborders and families. 



We agree with Spuler iu rejecting Kedteubacher's system, wliich is partly based on Adolph's 

 untenable theory of convex aud concave veins, but. more especially for the reason that 

 liedteubacher assumes that the primitive form of venation is that of the Epliemerid;e. lie 

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

 Jan-shaped form, as the May flies." It may be obj^'cted to this that the Ephemerida', though iu 

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

 .si)ecialized. That this is the case is also suggested by tbe 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 tliat iu 

 them a high degree of modirtcation has takeu place. Thus the two pairs of wings are very unlike 

 in size and shape, and this feature is a secoiulary one. Ilence the large number of niaiu 

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

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

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



Kedtenbacher regards the eleven longitudinal veins (I-XI) of Ei)hemerids as the normal 

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

 l)ro(!ess of reduction. This view has been adopted by Oomstock in his suggestive paper, 

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

 Spuler) uot being of primaiy importance. On the other hand, Kedtenbaclier's use of Konuiu 

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

 branches, is very convenient. 



Spuler divides the wings of each pair into an outspread portion {Spreitciithcil) and a folded 

 part (Falteutheil). The veins of the former area he numbers in the same manner as Kedtenbacher, 

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

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

 with the Greek letters cy fi. lie considers that Uagen was right in believing the I'hryganida', 

 Tipulariie, and some Microlepidoptera to be forms with a schematic, i. e., jirimitivo venation 

 (Stettin. Ent. Zeit., p. :nv,, ISTO). 



Spuler shares the opinion of Fritz Midler (Termitida'), IJrauer and Kedtenbacher (Libellulida-), 

 iind Haase (Papilionid*), that the costa is only a hypo'lcrinal structure, a thickening of the edge, 

 which does not have a tracdiea as its origin (Anlage), and wliicli tliercfore has nothing to do with 

 ithe veins. 



