12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



The wing is a thin, colorless, transparent and hairy membrane. 

 It is supported by chitinous tubes, the so-called veins. The " venous " 

 system formed by them consists of eight longitudinal tubes radiating 

 in a fan-shaped manner from the wing-root, and of a number of 

 transverse tubes, here and there connecting the longitudinal ones 

 with each other. All these tubes (veins) diminish distally in width. 

 The first longitudinal vein lies in the anterior margin of the wing. 

 The longitudinal veins extend in the crests of the folds, but not all 

 fold-crests are supported by veins. 



The principal contributions to our knowledge of the anatomy of 

 the wings of Diptera are by Redtenbacher (1886) and Adolph 

 (1885). These distinguished investigators described the systems 

 formed by the so-called " veins " and introduced a uniform nomen- 

 clature of the same, but they disregarded the other features of the 

 wings. Adolph (loc. cit.), especially, has worked out a uniform 



Fig. I. Diagrammatic profile view of the wing seen from before, showing 

 the warping; gi, marginal vein. 



scheme for the venation. He says that the wings of all Diptera 

 agree in respect to the venation, and that they differ only by the 

 veins being often replaced by folds, and vice versa. To investigate 

 how far he may be right was foreign to the task before me. I shall 

 use for the veins the designations proposed by Adolph {loc. cit.), 

 and append in brackets those of Lowne (1890- 1895). 



Adolph (1885) divides the wing into three regions: an anterior 

 one, the antica ; a middle one, the media; and a posterior one, the 

 postica. The antica is indicated by a, the media by m, and the 

 postica by p. The veins are distinguished by the letters b or a, ac- 

 cording to whether they lie in the crest of folds that rise above 

 (convex folds) or sink below (concave folds) the general wing 

 surface. If more than one vein (or fold) arises in a region the 

 veins (folds) are distinguished by Roman numerals. The most 

 anterior or marginal vein is not included in this system, but has its 

 own designation {gi). In this article Adolph's designations will 

 be employed. 



