[7] Leydig. Vom Bau des Thierischen Körpers (1864), Tafeln zur vergl. Anatomie (1864), Untersuchungen zur Anat. und Histologie der Thiere (1883), &c., besides many special memoirs in Müller’s Archiv., Zeits. f. wiss. Zool., Nova Acta, &c.
[8] In some Insects there are traces of a fourth thoracic segment.
[9] So also in some larvæ (Calandra, Œstrus, &c.).
[10] In some aquatic Insects the exchange of gases is effected by “pseudobranchiæ,” and the tracheal system is closed.
[11] Dragon-flies have the male copulatory apparatus, but not the genital aperture, in the fore part of the abdomen.
[12] Aphis and Cecidomyia are at times viviparous, and a viviparous Moth has been observed by Fritz Müller (Trans. Entom. Soc. Lond., 1883).
[13] For descriptions of the species Fischer’s Orthoptera Europæa (1853) or Brunner von Wattenwyl’s Nouveau Système des Blattaires (1865) may be consulted. The classification adopted by the last-named author is here summarised.
Blattariæ.
A.—Femora spinous (Spinosæ).
Fam. 1.—Ectobidæ. Seventh abdominal sternum undivided in female. Sub-anal styles absent in male. Wings with triangular apical area. Ectobia, including E. lapponica (Blatta) and other genera.