. Elementary text-book of zoology. Zoology. from one another by soft connecting membranes. They are coin- posed of simple dorsal and ventral plates, which are also connected laterally by soft membranes. This structure of the abdomen, which contains the respiratory and genital organs, permits of its being dilated and contracted (respiratory movements, distension of the ovary). Very often the posterior segments have a special struc- ture, owing to the various appendages which are con- nected with the processes of copulation and of depo- sition of the eggs. The anus is usually placed on the last
. Elementary text-book of zoology. Zoology. from one another by soft connecting membranes. They are coin- posed of simple dorsal and ventral plates, which are also connected laterally by soft membranes. This structure of the abdomen, which contains the respiratory and genital organs, permits of its being dilated and contracted (respiratory movements, distension of the ovary). Very often the posterior segments have a special struc- ture, owing to the various appendages which are con- nected with the processes of copulation and of depo- sition of the eggs. The anus is usually placed on the last abdominal ring, while the generative open- ing which is separate from the anal aperture opens on the ventral surface of the preceding segment (tig. 437). Terminal appendages, such as jointed filaments, etc., are present on the anal segment. The ap- /»-inllces genitales, forming the genital armature, are, on the con- trary, placed on the ventral side around the genital open- ing. Developed in the male as valves and in the female in the form of ovipositors, stings, etc., they arise from the imagiiial discs (growths of the hypodermis), in the Hymenoptera and Orthop- FIG. Posterior end of body of a Beetle. (Pterostichits $) (after Stein). 8, 9, Dorsal plates 8' 9', ventral plates; St, stigma; A, anus; G, genital tera on the eighth pair) and ninth (second pair) segments of the ab- domen (fig. 438). The ovipositors of the Diptera, on the other hand, are to be derived from the re- tracted posterior segments. Alimentary canal (figs. 439, 440).—The mouth, which is covered by the upper lip, usually leads into a narrow G'sopha- gus, into the anterior portion of which, distinguished as the buccal 34 I FIG. 438.—<i, Hind end of abdomen of a young female Locuttu with the protuberances of the ovipositor and the anal styles ; C' and C'', the internal and external protuberances of the penulti- mate ; C"', the same of the antepenultimate seg- ment, b, slightly older
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
