The New Zealand Railways Magazine, Volume 7, Issue 2 (June 1, 1932)
Entomology—a Most Fascinating Study — (Introductory.)
It may truthfully be asserted that Nature provides us with a most scientific and fascinating field of research beneficial to the economic welfare of the world. “To eat and avoid being eaten,” is Nature's fundamental law. Woe betide us should we dare to interfere so as to in any way upset the compensating balance of her law. To plagiarise the writer of “David Harum” we may say:
“All fleas have lesser fleas to bite em,” “And so the world wags on—ad infinitum.”
When man interferes with Nature's order he courts disaster. In Jamaica the brown rat came over in ships and, escaping to land, wrought havoc amongst the sugarcane fields. In order to cope with the rat pest the planters imported the Indian mongoose, an animal closely allied to the stoat but fiercer and more fearless. The mongoose soon wiped out the brown rat; then, failing natural prey, the snake, turned its attention to the ground nesting birds, with the result that noxious insects multiplied rapidly and the cure was worse than the disease.
The stoat and weasel were brought into New Zealand to keep down the rabbit—also an importation. Our ground native birds are, in many cases, becoming almost extinct and Nature's balance is being upset. The fox was imported into Australia for the same reason—the rabbit—and has turned out a veritable lamb slayer.
To a great extent the economic welfare of the world is governed by insect life. Insects are very fertile, and had Nature not provided “enemies,” or “parasites,” to provide a check upon them, the world might soon be over-run by different varieties, and the science-predicted war between man and insect already a fait accompli.
It is intended to deal with our insects in short articles to follow this introduction, not at any length, but briefly and descriptively.
To begin with, insects are articulate creatures, comprising seven distinct orders, viz:—
- 1. Coleoptera or “sheath” winged, such as beetles.
- 2. Diptera or two winged, the lower pair of wings being represented and replaced by “poisers,” such as the glowworm.
- 3. Hemiptera or gauze winged, such as plant-lice.
- 4. Hymenoptera, with organs for masticating, such as bees.
- 5. Lepidoptera, moths and butterflies. Certain members of this order do not feed in the “perfect” state the food organs being completely absent.
- 6. Neuroptera, gauze and articulate winged, such as “lace-wings.”
- 7. Orthoptera, having all four wings of an equal size. These are divided into terrestial and aquatic groups, as the stick insect and dragonfly. In this “order,” which is not large, in many instances the mature insect is apterous and the life changes a series of moultings.
The body of all insects comprises three parts; head, thorax and abdomen. On the head are two kinds of eyes—simple and compound. The latter are composed of a large and varying number of six-angled facets, each an eye itself, giving the insect a completely all round vision. The “simple” eyes are three, and disposed between the compound pair; in some forms they are absent. The antennae are two eight jointed organs at each side of the head and rising from between the eyes. The mouth consists of upper and lower lips, jaws and mandibles. This organ differs greatly in “sucking” insects.page 63
The “thorax” has three divisions to each of which is attached a pair of legs at the underneath; the fore wings to the second division, the back wings to the third on the upper surface.
“The “abdomen” has nine segments—in many cases some are absent—embracing the “nourishing,” articulate and genitive organs. In “sucking” forms, the “crop,” or stomach, is formed of a small bag attached to a thin duct connecting with the insect's throat, and works on the vacuum principle. The heart is tube-like and along the back. It is composed of numerous chambers through which the blood is pumped to the head by a process of contraction and expansion.
The breathing system has many tubes that take in the necessary air from openings at the sides of the insect, and called “spiracles.” The “nerye” system is an intertwined chain traversing the stomach surface and taking the place of the “spinal cord” in animals of a higher organisation.
The life changes, known as “metamorphosis,” are four in number, and the most essential feature of insect life: viz., “egg,” “larva” or “grub, “pupa” or “chrysalis,” “imago” or “perfected insect.”
The eggs shew a great diversity as to shape and colour in the different forms. These are laid by the mother, instinctively and unerringly, on substances necessary for feeding purposes of the embryonic larvae, whose time will be truly taken up with feeding.
In the spring of the year, some readers may feel disposed to delve into this fascinating study themselves, and in so doing not only derive great pleasure but, perchance, make some discovery of much value to scientific research.