Devaux, H. Vom Ersticken durch Ertrinken bei den Tieren und Pflanzen. (Naturwiss. Rundschau, vi Jahrg., 1891, p. 231; Compt. rend. Soc. de Biol., 1891, Ser. 9, iii, p. 43.)
See also Dewitz, p. 482; Kolbe, p. 482.
THE ORGANS OF REPRODUCTION
Insects are without exception unisexual, the male and female organs existing in different individuals, no insects being normally hermaphroditic. The reproductive organs are situated in the hind-body or abdomen, especially near the end, the genital glands opening externally either in the space between the 7th and 8th, or 8th and 9th, or 9th and 10th abdominal segments, but as a rule between the 8th and 9th segments (Fig. 299).
The primary or essential male organs are the testes, those of the female being the ovaries. As we shall see, the primitive number of seminal ducts and oviducts was two, this number being still retained in Lepisma and the Ephemeridæ. The reproductive organs of both sexes are at first, in their embryonic condition, of the same shape and structure, becoming differentiated in form and function before sexual maturity. These glands and ducts have a paired mesodermal genital rudiment, the ends of the ducts being often connected with corresponding ectodermal invaginations of the cuticle.
The secondary sexual organs mainly comprise the external genital armature of the male, and the egg-laying organs, or ovipositor of the female. Besides these structures there are other more superficial secondary sexual characters, such as differences in the size and ornamentation as well as coloring of the body, or of parts of it.
The primary sexual organs of insects have been conveniently tabulated by Kolbe, thus:—
I. Male reproductive organs.
1. Two testes, with testicular follicles.
2. Seminal ducts (vasa deferentia).