. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. 20 INJURIOUS AND USEFUL INSECTS salivary glands and Malpighian tubules of insects are bathed in the blood, and not injected with blood, as in higher animals, probably explains their diffuse form. By tearing away the fat-body bit by bit the student will bring into view the two large tracheal tubes which run along the sides of the body. They send out branches to all the viscera, and com- municating branches to one another, besides receiving short branches from the spira

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. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. 20 INJURIOUS AND USEFUL INSECTS salivary glands and Malpighian tubules of insects are bathed in the blood, and not injected with blood, as in higher animals, probably explains their diffuse form. By tearing away the fat-body bit by bit the student will bring into view the two large tracheal tubes which run along the sides of the body. They send out branches to all the viscera, and com- municating branches to one another, besides receiving short branches from the spira
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Image ID: PG4AG5
. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. 20 INJURIOUS AND USEFUL INSECTS salivary glands and Malpighian tubules of insects are bathed in the blood, and not injected with blood, as in higher animals, probably explains their diffuse form. By tearing away the fat-body bit by bit the student will bring into view the two large tracheal tubes which run along the sides of the body. They send out branches to all the viscera, and com- municating branches to one another, besides receiving short branches from the spiracles. Cut out a piece of a tracheal trunk, and examine it with the microscope. Notice the spiral thickening of the lining cuticle; the silvery or dark appearance of the tubes varies according to the direction in which the light falls upon them, and is due to contained air. Clear the nervous system. Note the ganglia and the connectives which unite them. Follow the nerve cord into the head. The dissection is too difficult for an unpractised hand. The head must be fixed to a block of paraffin with one side uppermost. See that the head is dry externally; then melt the paraffin in one place with a piece of hot metal, and lightly press the head against it. Dissect away the side of the head. In front will be seen the brain, which gives off two very short connectives to the sub-oesophageal ganglion. A chitinous plate, the tentorium, is interposed, through which the con- nectives pass. The oesophagus lies upon the tentorium, and passes between the connectives. In a female cockroach the ovaries, which lie in the hinder part of the abdomen, may be cleared and examined. Each. Fig. i8.—Nervous system of female cockroach.. 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 work.. Miall, Louis Compton, 1842-. London, G. Bell &

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