In using a book of this type it is essential to understand the method of naming animals. The scientific study known as systematics is concerned with naming animals and plants, and with arranging them in groups which indicate their relationships with one another.
Modern systematics is based on the work of the Swedish naturalist Carl von Linne (1707-1778), also known as Linnaeus. He gave all the then known plants and animals a Latin name and arranged them in groups according to their physical appearance. He chose Latin because at that time this was the international language of science.
The principles of nomenclature established by Linnaeus are still in use today. The Latin or scientific name of an animal or plant consists of two parts, the first denoting the genus (plural genera), the second the species. In the present book it is necessary to use the scientific names because many of the animals mentioned do not have common English names, and when these do exist they are often not standard throughout the country. For example, the song thrush is known in Scotland as a mavis.
In 1859 a book was published which has had a profound effect on man’s understanding of the world around him.
This was The Origin of Species, by the English scientist Charles Darwin (1809-1882), who put forward the theory of natural selection, which seeks to explain how all existing species have evolved from species which have existed in past ages. Since Darwin’s time systematics has become more than a means of naming animals and plants; it has in many cases shown their relationships by grouping together those which are thought to have evolved from a common ancestor. The animal kingdom has been divided into some 14 major groups, known as phyla (singular phylum). Only a few of these have representatives occurring indoors, namely worms, molluscs, arthropods and vertebrates. The worms are represented in houses only by earthworms. The molluscs, a group that includes snails and bivalves, are not normally found in houses, except for certain slugs that occur in cellars.
The vertebrates or animals with a vertebral column include fishes, amphibians, reptiles, birds and mammals, including of course man.
Arthropods are animals with jointed legs. The group contains the crustaceans, scorpions, millipedes, centipedes, mites, spiders and last but not least the insects. About one million animal species have been described and more than three- quarters of these are arthropods. It is not surprising, therefore, that most of the animals found in houses belong among the arthropods.