A treatise on some of the insects of New England which are injurious to vegetation / by Thaddeus William Harris.

  • Harris, Thaddeus William, 1795-1856.
Date:
1852
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on some of the insects of New England which are injurious to vegetation / by Thaddeus William Harris. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    The word Insect, which, in the Latin language, from whence it was derived, means cut into or notched, was designed to express one of the chief characters of this group of animals, whose body is marked by several cross-lines or incisions. The parts between these cross-lines are called segments, or rings, and consist of a number of jointed pieces, more or less movable on each other. Insects have a very small brain, and, instead of a spinal marrow, a kind of knotted cord, extending from the brain to the hinder extremity; and numerous small whitish threads, which are the nerves, spread from the brain and knots, in various directions. Two long air-pipes, within their bodies, together with an immense number of smaller pipes, supply the want of lungs, and carry the air to every part. Insects do not breathe through their mouths, but through little holes, called spiracles, generally nine in number, along each side of the body. Some, however, have the breathing-holes placed in the hinder extremity, and a few young water-insects breathe by means of gills. The heart is a long tube, lying under the skin of the back, having little holes on each side for the admission of the juices of the body, which are prevented from escaping again by valves or clappers, formed to close the holes within. Moreover, this tubular heart is divided into several chambers, by transverse partitions, in each of which there is a hole shut by a valve, which allows the blood to flow only from the hinder to the fore part of the heart, and prevents it from passing in the contrary direction. The blood, which is a colorless or yel- lowish fluid, does not circulate in proper arteries and veins; but is driven from the fore part of the heart into the head, and thence escapes into the body, where it is mingled with the nutritive juices that filter through the sides of the intestines, and the mingled fluid penetrates the crevices among the flesh and other internal parts, flowing along the sides of the air- pipes, whereby it receives from the air that influence which renders it fitted to nourish the frame and maintain life. Insects are never spontaneously generated from putrid animal or vegetable matter, but are produced from eggs. A few, such as some plant-lice, do not lay their eggs, but retain them within