. Animal biology. Zoology; Biology. 276 METAZOAN PHYLA of apparatus used in copulation, egg laying, or stinging. This results in a lessening of the apparent number of metameres. 311. Internal Structures.—The body cavities of an insect are not truly coelomic but are parts of a hemocoel. A heart lies under the dorsal wall of the abdomen and blood circulates through these hemocoelic spaces. The circulation is not so important as in most animals, however, since it plays practically no part in respiration. When the body of an Base of antenna Subesophageal^ ganglia Supra esophageal ganglia or brain
. Animal biology. Zoology; Biology. 276 METAZOAN PHYLA of apparatus used in copulation, egg laying, or stinging. This results in a lessening of the apparent number of metameres. 311. Internal Structures.—The body cavities of an insect are not truly coelomic but are parts of a hemocoel. A heart lies under the dorsal wall of the abdomen and blood circulates through these hemocoelic spaces. The circulation is not so important as in most animals, however, since it plays practically no part in respiration. When the body of an Base of antenna Subesophageal^ ganglia Supra esophageal ganglia or brain Compounal eye ?Pharynx Honey sac Thoracic ganglia. Digestive stomach Ma/pighran tubules Ventral nerve cord Rectal glands Hind gut Fig. 175.—A honeybee dissected to show the digestive, nervous, and tracheal systems. (From Leuckart wall chart.) Illustrates the digestive system of a suctorial insect. insect is opened, many white glistening tubes are seen. These are the tracheae. They are held open by rings of chitin, branch repeatedly, and the finer branches reach all parts of the body. In insects of active flight the tracheae are dilated in certain places and form air sacs (Fig. 175). By means of this system of tubes oxygen is conveyed directly to the tissues of the body and carbon dioxide is carried away. Although the blood contains both oxygen and carbon dioxide it is only in the amount that any tissue would have. In some cases aquatic forms do not possess gills, but water is taken into the posterior end of the alimen- tary canal, the wall of which is lined with papillae supplied with tracheal Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wolcott, Robert Henry, 1868-1934. New York ; London : McGraw-Hill Book Company, Inc.
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