HISTORICAL DISCUSSION." As is the case with other groups of insects the names applied to the wing veins of aphids were given in the first place without homological reference to the veins of other insects. That is, we have an arbitrary system which has no significance outside the family of Aphididæ. Recently several papers have appeared which rename the wing veins with this aim in view, but as the true homologies of the wing veins themselves have not heretofore been established, certain mistakes in applying the ComstockNeedham nomenclature have, of necessity, arisen. These papers. will be discussed in turn. First, however, it would seem of interest to review the earlier terminology. For convenience in this discussion attention is called to Fig. 8, in which the names are used as based upon the homologies revealed in the study of the tracheation of the wings as recorded in this paper. The following table will show the relation of the ComstockNeedham terminology to the terminology previously in use for the wing veins of aphids: *For careful general historical discussion of studies of wing-venation see MacGillivrary, A. Ď. ('06). Wings of the Tenthredinoidea. PP. 570–574. The interpretation of the so-called subcostal has been* that it is a single heavy vein spreading at the distal portion into the stigma. That this interpretation is incorrect the foregoing discussion on the tracheation has made clear. It is really a composite structure bordered along the cephalic margin by the subcostal vein and containing the radius and the coalesced proximal portions of the remaining wing veins. It will be seen by reference to the accompanying table that the first, second and third discoidals are respectively the 1st Anal, Cubitus and Media. The second anal not persisting in the adult wing (that is, it is represented only by a constantly appearing trachea which soon clears) is not shown in any published figures of aphid wings. In the hind wings the first and second discoidals are respectively (fig. 8) the cubitus and media, and the so-called subcostal vein is the radial sector. Redtenbacher† gives homologies of the wing veins of aphids and psyllids, which except for his interpretation of alternate convex and concave veins, come pretty close to the conclusions arrived at from the study of the tracheation. Except for Sc and vein VI in the forewing and that Sc is not accounted for in the hind wing his psyllid wings are correct. His difficulties with the aphid wings could not be settled without reference to the tracheation. Handlirsch gives the only figure of wing trachea for psyllids or aphids published previous to this present paper. His interpretation of the trachea for the wing pad of the psyllid nymph is practically the same as that given in this paper. With the freshly emerged wing of Schizoneura langigera, however, three mistakes occur. The line which he indicates as the subcostal trachea does not occur as a trachea but as a well defined fold of the subcostal vein. (See page 108). The unbranched trachea which he considers M is really Cu. and his Cu. is one of the anals. The question in regard to M. and Cu. however could only be settled by the testimony of the tracheation of the wing pad. (See page 113 and fig. 21). * Oestlund, O. W. Aphididae of Minnesota, p. 4. 1887. † Redtenbacher, Josef. Ann. k. k. Naturh. Hofmus., I. 1886. Handlirsch, Anton. Die Fossilen Insekten und die Phylogenie der Rezenten Formen. 1906-08. Handlirsch homologizes the veins of the Phytophthires which he figures and also names what trachea he figures. In Woodworth's discussion of the wing veins of Phytophthires* the veins of these insects are homologized to the extent that the statement is made that the front wing of Aleurodidæ is the same in its maximum condition of venation as the maximum of the hind wings of Aphidæ, and the hind wings the same as the minimum of Aphidæ, and that the venation of the front wing of Coccidæ is the same as the minimum of the front wing of Aleurodida. This author figures wings of all the Phytophthires he discusses but as the wing veins are not labeled and it is not apparent from the text which of the "independents" he interprets the media and the cubitus to be either with the psyllids or aphids it is not possible to homologize them from his figures. The meaning of his statement that in only the Psyllida is the venation extensive enough to show clearly their affinity to the higher Homoptera is not apparent, as his maximum number of veins for the aphids according to his figures exceeds the maximum for the psyllids; and the number when the minimum is taken is the same for both wings except for one extra branch for the psyllids. Exception, moreover should be taken to his diagram of the venation of the Aphididæ, for the "additional independent and the cross vein at the tip" which he states are very rarely present, are never present in fact in the normal venation of any species of aphid. And if abnormal or freak veins are to be included in the venation of aphid wings there would be no reason to stop at these two, for cubitus might be branched, any of the branches of media have an extra fork and "cross-veins" might be almost indiscriminately located as between cubitus and the first anal. In a very convenient classification of some of the external characters of Aphididæ Mr. Vickery† attempts a homology of the wing veins of aphids with those of other insects, stating that the names he gives, based upon Comstock's system, were decided upon from a study of other reduced wings such as Psocus, and from a study of the abnormal venations found so frequently in plant-lice. Mr. Vickery's homologies are based upon the comparison of mature wings and the misinterpretations which have * Woodworth, C. W. ('06). The Wing Veins of Insects. pp. 124–125. † Vickery, R. A. ('08). A Comparative Study of the External Anatomy of Plant-lice. arisen are readily explained by this fact. Perhaps in no other family could be found a clearer demonstration of the value of the study of the tracheation in this connection. SUMMARY. The introductory discussion outlines the reasons for undertaking this study of wing vein homologies, states the conditions under which the study has taken place, and mentions some of the difficulties involved in the manipulation of this sort of material. Attention is called to the coalescence of trachea both the nor mal occurrence and some unusual instances. All the veins present in the four families discussed are homologized, each being taken up for detailed consideration and the tracheal basis for the homologies being carefully stated. The historical discussion includes a notice of all such published work as has any direct bearing upon this present paper. All the main features of venation or tracheation discussed are illustrated by the accompanying figures. Buckton, G. B. Comstock, J. H. Comstock, J. H. Comstock, J. H. 1906–1908. BIBLIOGRAPHY. Monograph of British Aphides. and Needham, J. G. Wings of Insects. Die Fossilen Insekten und die Phylogenie der Rezenten Formen Kuwayama, I von S. Die Psylliden Japans. Trans. of Sappro Natural Hist. Society. 1907-08. Loew, F. Gen. Aphalara et Rhenocola. Taf. XI.) 1882. (Zoologisch Botanische Wien Loew, F. Mittheilungen über Psylloden. Verh. z.-b. Wien XXIX, pp. 549– 598. Loew, F. pl. XV. 1879. Psylloden. Taf. IX. (1878.) Verh. z.-b. Wien XXVIII. Revision der palaarktischen Psylloden in Hinsicht auf Systematik und Synonymie. Verh. z.-b. Wien XXXII, pp. 225–254. 1882. Loew, F. Loew, F. Zur Biologie und Charakteristik der Psylloden nebst Beschreibung zweier neuer Species der Gattung Psylla. Verh. z.-b. Wien, XXVI, pp. 187-216. pls. 1 and 2, 1876. Loew, F. Zur Systematik der Psylloden. Verh. z.-b. Wien, XXVIII, pp. 586610, pl. IX. (Figures of the neuration of 11 genera) 1878. MacGillivray, A. D. A Study of the Wings of the Tenthredinoidea. Proceedings of the Nat. Museum. Vol. XXIX. 1906. Oestlund, O. W. Aphididæ of Minnesota. 1887. Packard, A. S. 5th Report Ent. Commission. Redtenbacher, J. Flugelgeader der Insecten. Ann. k. k. Naturh. Hofmus. I. 1886. Riley, C. V. Notes on N. A. Psyllida. Biological Society of Washington, 1883. Sanborn, C. E. Kansas Aphididæ. Schwarz, E. A. Entomological Soc. of Washington. 1902–04. North American Psyllida. Notes on Scott, J. Monograph of the British species belonging to the Hemiptera-Homoptera, family Psyllida; Tr. E. Soc. 1876. pp. 525–569, pls. VIII and IX. Scott, J. On certain Genera and Species of the Group of Psyllidæ in the collection of the British Museum. 1882. Trans. Ent. Soc. London. 1882. pp. 449-473. Plates XVIII, XIX. Scudder, S. H. Fossil Insects. Vickery, R. A. A Comparative Study of the External Anatomy of Plant Lice. 1908. Woodworth, C. W. The Wing Veins of Insects. 1906. EXPLANATION OF PLATES. The figures submitted have been selected from numerous ones prepared in the progress of this study. In their preparation two methods were employed. The figures showing tracheation are from camera lucida sketches verified or corrected by examination of each significant point through a high power lens,— oil emersion when necessary. The figures giving venation (except Fig. 29) are ink tracings of photographs, the blue prints which were used being bleached after the drawings were made in order that black and white figures uniform with the camera lucida sketches might be secured. PLATE XVI. FIG. 1. Lachnus strobi (Fitch). Tracheation of wing of newly emerged aphid. See page 111. FIG. 2. Melanoxanthus sp. Wing of newly emerged individual showing an unusual case of coalescence of trachea, See page 107. FIG. 3. Myzus cerasi (Fab.) Tracheation of wing of newly emerged aphid. See page 110. FIG. 4. Aphis species. Tracheation of wing of newly emerged aphid showing connection with the body trachea. The region of the costal vein and also the main vein channel of the wing indicated here. See page 108. FIG. 5. Callipterus ulmifolii Monell. Tracheation of wing of newly emerged aphid. FIG. 6. Chaitophorus nigra Oestlund. Tracheation of wing of newly emerged aphid. See page 116. FIG. 7. Chaitophorus populicola Thos. Tracheation of hind wing of newly emerged aphid. Typical, showing connection with body trachea. See page 116. FIG. 8. Macrosiphum solanifolii Ashmead. Venation of both wings. FIG. 9. Macrosiphum pisi. Tracheation of hind wing of newly emerged aphid. Very exceptional. See page 116. PLATE XVII. FIG. 10. Microparsus variabilis Patch. Venation of both wings. Venation of this species very unstable. The type figured is a common one. FIG. 11. Toxoptera graminum Rond. Venation of both wings. FIG. 12 and 13. Pemphigus acerifolii Riley. Tracheation of fore and hind wings of newly emerged aphid. See pages 109 and 117. FIG. 14. Pemphigus venafuscus Patch. Venation of both wings. emerged aphid. See page 114. FIG. 16. Hamamelistes spinosus Shimer. Venation of both wings. FIG. 18. PLATE XVIII. Mindarus (abictinus Koch ?). Tracheation of wing pad of nymph. See page 115. FIG. 19. Mindarus (abietinus Koch ?). wing. Mindarus (abietinus Koch ?). wing. Tracheation of freshly emerged Venation of both wings. See Tracheation of wing pad of nymph. Tracheation of freshly emerged Venation of both wings. |