Frisch Twelve Little Housemates

Enlarged and Revised Edition of the Popular Book Describing Insects That Live in Our Homes
1. Auflage 2013
ISBN: 978-1-4831-4714-7
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 156 Seiten

Twelve Little Housemates focuses on the characteristics, health hazards, life cycle, feeding habits, transfer, and control of insects that generally live in the house. The manuscript first offers information on the house-flies, and particularly emphasized are the distinguishing characteristics of these insects from other insects, their life cycle, how they can be health hazards, and how they are considered in the medical field. The text also examines the different species of lice and their preferences, including the ways they are transferred and controlled. The book focuses on the appearance, feeding habits, and control of cockroaches. The feeding habits and control of ants and bed-bugs are also discussed. The text also elaborates on the life cycle, appearance, characteristics, and health hazards of spiders, ticks, and gnats. The protection measures and control procedures against these insects are underscored. The manuscript also focuses on fleas and clothes moth. The text is a dependable source of information for readers wanting to be familiar with common insects in the house.

Autoren/Hrsg.

Frisch, Karl Von

Leseproben

Gnats

Publisher Summary

This chapter discusses gnats, the common mosquitoes of America. Gnats have only two wings and therefore, they are flies. As with all members of this group, the hind-wings are represented by small balancers. The gnat, too, has salivary glands; after it has pierced the skin, it deposits through the proboscis a tiny drop of liquid, which acts as a poison. It irritates the surrounding tissues and quickly produces a local inflammation. This is connected with an expansion of the blood vessels, which in turn leads to an increased flow of blood, as the redness round the puncture shows. It is only the female gnats that suck blood. Gnats constitute a pest only near accumulations of water. The females lay their eggs on the surface of water, many species lay also on damp ground when the eggs are washed into puddles by rain. When the larvae emerge, they dive down into the water and stay there during the entire period of development. The larvae are harmless vegetarians and make do with some decaying vegetable matter. One end of their bodies has access to the air, from which they have come, for their respiratory organs must be supplied with air under water too. The larvae of common gnat breathe in the air through a fine tube, by which they are usually suspended from the surface.

Gnat. Starting to bite (). Replete at the end of the bite (). The proboscis, for biting and sucking, lies in a sheath which is open at the front and which bends backward in a loop when the proboscis is in action. The lower end of the sheath acts as guide and support while the skin is being pierced.

Gnats, the common mosquitoes of America, are “flies”, too. It is true that their tapering, slender body and their long, fine legs make them look different from the stout bluebottles. But we must not let ourselves be misled by mere looks. Gnats have only two wings and therefore they are flies. As with all members of this group, the hind-wings are represented by small balancers. When one is in the right mood, solitary specimens of the house-fly may not be unpleasant. But gnats—sometimes called midges—can never be pleasant. They have a treacherous—and often silent—mode of attack and we don’t feel them piercing our skin with their fine proboscis, but their bites itch all the more intensely.

Why gnat bites itch

Many people classify animals as either useful or harmful. Actually they are surprised that there is such a thing as a harmful animal: they simply cannot get rid of the idea that man walks the earth as the centre of creation and that everything else is there merely to serve him.

Anyone who looks round with open eyes will form a very different picture. He will notice that the humblest of living creatures are just as well equipped for the hard struggle for existence as the arrogant human race. We have already seen that the insect’s breathing organs compare not unfavourably with our own; in gnats the organs of flight reach a high level of perfection, and every mechanic must admit that their proboscis is a masterpiece of ingenuity as regards both structure and mechanism. Why has Nature decreed that their bites should itch? Would it not be better for them if their contact with us were painless? We should not then have any occasion to swat them when we catch them biting us. There is plenty of evidence, however, to show that the irritation we feel is only the necessary consequence of an arrangement that is very convenient for the gnat.

The sight of a delicious dish makes our mouth water, which is only a short way of saying that the very sight of food stimulates our salivary glands to produce the secretion that helps us to swallow and digest it. The gnat, too, has salivary glands, and its mouth waters when it settles to have a meal off us, though here the purpose is different: after it has pierced the skin, it deposits through the proboscis a tiny drop of liquid, which acts as a poison. It irritates the surrounding tissues and quickly produces a local inflammation. This is connected with an expansion of the blood vessels, which in turn leads to an increased flow of blood, as the redness round the puncture shows. We feel the effect of the poison as pain, and that may be fatal for the gnat. And yet this droplet, so inconvenient to us, is essential to the gnat, since it alone makes it possible for the hair-like proboscis to get at the food. In addition, the gnat’s saliva has the extraordinary property of preventing the blood from congealing, so that the narrow passage of the proboscis cannot be blocked by any clot.

It is lucky for gnats that cattle are not so sensitive as we are. In spite of the irritation caused by their bites, they are often allowed to finish their meal in peace.

General remarks on blood-sucking

In a certain sense gnats are specialists as far as food is concerned. We never see them settling like house-flies on sugar or bread, on meat or unsavoury waste matter. They want to feed on blood, and it must be that of warm-blooded animals. Newts or lizards are not good enough for them, but they are not particular whether they get their nourishment from a human being, or a cow, or a bird. Man is by no means their only victim. When considering their lust for blood we must make one important reservation: it is only the female gnats that suck blood. Nor are they a reprehensible exception in this respect, for there are other similar cases. Blood-sucking gad-flies, for instance, which often spoil the pleasure of bathing, and other big, fat horse-flies, sometimes a plague near cattle pastures, are always females. The males disport themselves on flowers and sip honey.

Is this because the females have a particularly malicious temper? Not really. There is good reason for this difference in the activities of the sexes. The female needs her meal of blood to bring her eggs to maturity.

How a pest on land comes originally from water

Gnats constitute a pest only near accumulations of water, and the reason is not far to seek: they must have water if they are to reproduce. The females lay their eggs on the surface of water (see figure on p. 27); many species lay also on damp ground, whence the eggs are washed into puddles by rain. When the larvae emerge, they dive down into the water and stay there during the entire period of development. Under favourable conditions this takes only about a week, but considerably longer if the weather is cool or food is scarce. In contrast to their mother, the larvae are harmless vegetarians and make do with some decaying vegetable matter; many species prefer animal food, and the myriads of tiny creatures living in the water provide a varied bill of fare.

The eggs of the gnat, or common mosquito, float all in a clump on the water like a toy boat. The larva () and the pupa () live in the water, but breathe air on the surface through tubes. (Magnified about 7 times.)

One end of their bodies has access to the air, from which they have come, for their respiratory organs must be supplied with air under water, too. The larvae of our common gnat breathe in the air they require through a fine tube, by which they are usually suspended from the surface (see figure). From here they wriggle down below on occasional voyages of exploration.

The pupae of the gnat are not the barrel-shaped hard cases characteristic of house-flies. On the contrary, they are lively little devils. While the larva is supplied with oxygen from the rear, the pupa has two short breathing-tubes perched like horns on its head end (see figure on p. 27). After two or three days in the pupal stage, the winged insect emerges. It floats about on the raft-like empty pupa case until its wings are dry and strong enough to carry it ashore.

The swarms of dancing midges or gnats which sometimes rise in the air like smoke consist exclusively of males. The females only dart in to snatch a mate and to elope with him for the brief nuptial flight.

Brackish water, ponds and pools, even small puddles and water-butts are favourite breeding-places. Important as the water-barrel is for gardening, it is often a source of torment for those who frequent the garden. Only the cold of autumn checks the reproductive activity in many unheeded pools, which brings forth generation after generation of gnats to annoy us. When the weather gets colder, they seek protection indoors, above all in the cellars of houses, where thousands can be seen hibernating on ceilings and walls. So it is not till this season of the year, when mercifully they are not bloodthirsty, that they actually become our housemates.

The gnat or mosquito pest is worst in the tundra and watery plains of Siberia, Lapland and Northern Canada, where these insects make it practically impossible for man to settle, and in many countries of South America and Southern Asia: the notorious mosquitoes of these regions are very closely related to our gnats. It is easy to understand their abundance in the tropics, since they need water and love warmth. But it is not so clear why such swarms of them should be found in Arctic regions. In Lapland snow lies on the ground for eight months of the year. Why should these little pests feel so comfortable in a country where they will search in vain for cellars to protect them from the severe winter, where there is little rain during the short summer and where for miles...