—— De la faculté qu’out les mouches de se mouvoir sur le verre et sur les autres corps polis. (Archiv Museum Teyler (2), 4 Part, pp. 16. Fig.)
Simmermacher, G. Untersuchungen über Haftapparate an Tarsalgliedern von Insekten. (Zeitschr. f. wissensch. Zool. xl, 1884, pp. 481–556. 3 Taf., 2 Figs. Also Zoolog. Anzeiger, vii Jahrg., 1884, pp. 225–228.)
—— Antwort an Herrn Dr. H. Dewitz. (Ibid., pp. 513–517.)
Dahl, F. Die Fussdrüsen der Insekten. (Archiv f. mikroskop. Anat., 1885, xxv, pp. 236–263. 2 Taf. See also p. 118.)
Emery, C. Fortbewegung von Tieren an senkrechten und überhangenden glatten Flächen. (Biolog. Centralbl., 1884, 4 Bd., pp. 438–443.)
Léon, N. Disposition anatomique des organes de succion chez les Hydrocores et les Géocores. (Bull. Soc. des Medec. et Natur, de Jassy., 1888.)
d. The wings and their structure
The insects differ from all other animals except birds in possessing wings, and as we at the outset have claimed, it is evidently owing to them that insects are numerically so superior to any other class of animals, since their power of flight enables them to live in the air out of reach of many of their enemies, the greatest destruction to insect life occurring in the wingless larval and pupal stages.
The presence of wings has exerted a profound influence on the shape and structure of the body, and it is apparently due to their existence that the body is so distinctly triregional, since this feature is least marked in the synapterous insects. The wings are thin, broad leaf-like folds of the integument, attached to the thorax and moved by powerful muscles which occupy the greater part of the thoracic cavity. The two pairs of wings are outgrowths of the middle and hinder part of the thorax, the anterior pair being attached to the mesothoracic and the hinder pair to the metathoracic segment. The larger pair is developed from the middle segment of the thorax. The differentiation of the tergites into scutum, scutellum, etc., is the result of the appearance of wings, because these sclerites are more or less reduced or effaced in wingless insects, such as apterous Orthoptera and moths, ants, etc.
The size of the hinder thoracic segments is closely related to that of the wings they bear. In those Orthoptera which have hind wings larger than those of the fore pair, the metathorax is larger than the mesothorax. In such Neuroptera as have the hind wings nearly or quite as large as the anterior pair, or in the Trichoptera and in the Hepialidæ, the metathorax is nearly as large as the mesothorax, while in Coleoptera the metathorax is as large and often much larger. In the Ephemeridæ, Diptera, and Hymenoptera, which have either only rudimentary (halteres) or small hind wings, the metathorax is correspondingly reduced in size.