Acarina is the mite and tick order of the Arachnida. They have a rounded body with no demarcation between the prosoma and the opisthosoma. Research Acarina
Arachnida is a class of arthropods. They are the spiders, scorpions, king- crabs and mites. They have the body divided into a number of segments or somites, some of which have always articulated appendages (limbs, etc). There is often a pair of nervous ganglia in each somite, although in some forms (as spiders) the nervous system becomes modified and concentrated. They are oviparous and somewhat resemble insects, but they have a united head and thorax, and do not undergo a metamorphosis similar to insects. They respire by tracheae, or by pulmonary sacs, or by the skin. Research Arachnida
Articulata is the third great section of the animal kingdom according to the arrangement of Cuvier, including all the invertebrates with the external skeleton forming a series of rings articulated together and enveloping the body, distinct respiratory organs, and an internal ganglionated nervous system along the middle line of the body. They are divided into five classes, viz. Crustacea, Arachnida, Insecta, Myriapoda, and Annelida. The first four classes are now commonly placed together under the name of Arthropoda, and the whole are sometimes called Arthrozoa. Research Articulata
Scorpionidea or Scorpiones is the scorpion order of Arachnida. They have four pairs of lung-books in the mesosoma and the post-anal telson forms a sting. Scorpions are amongst the most hardy of animals, able to survive frozen in ice for three weeks, temperatures over 40 degrees Celsius and withstand two hundred times the amount of radiation (such as the fallout from a nuclear explosion) that kills other animals. Scorpions are deaf and nearly blind, but are very sensitive to earth vibrations and air vibrations, detected through feelers. Research Scorpionidea
Spider (Araneidae) is an order of animals of the class Arachnida, all having eight legs. Most spiders are terrestial, but some live in fresh water.
The spiders have a body that is divided into two parts: the head and breast, fused into one piece; and the abdomen, usually all in one piece, and only in rare cases with hints of segmentation. Between these two parts there is typically a narrow waist. The region corresponding to the head bears two pairs of mouth parts: a pair of two-jointed poison-jaws or chelicerae; and a pair of sensitive, usually six-jointed pedipalps.
All spiders have a poisonous bite, but the bite is not severe except in a few tropical forms. The poison of the bird-catching spider (Mygale) kills a bird in a few minutes. In male spiders the tip of the pedipalp is complicated, it becomes a reservoir for spermatozoa at the mating season, and is used to transfer them into the female, where they fertilise the eggs just prior to the eggs being laid. In the main the pedipalps are organs of touch, with very sensitive tactile qualities.
On the top of the head are several pairs of simple short-sighted eyes. From the region corresponding to the thorax there arise four pairs of seven-jointed legs, ending in minute curved claws, by means of which spiders grip the surface on which they creep. At the end of the abdomen there are between four and six minute appendages transformed into spinnerets, from which the silken threads emerge. Each spinneret resembles the rose of a watering-can, and contains numerous minute tubes known as spinning-spools through which the silk issues. There may be hundreds of these spinning-spools and each is connected with an internal gland which produces the silk. The gland is enclosed in a muscular envelope, the contraction of which acting like a syringe, forces the liquid silk down a duct and out at the spinning-spool. There are sometimes three kinds of glands, producing different kinds of silk, and it rests with the spider to use more or fewer at one time, thereby adjusting the thickness of the thread produced. The thread is a fusion of many jets of liquid silk, which solidifies instantly it is exposed to the air.
A small minority of spiders breathe by two pairs of lung-books; all the rest breathe by two lung-books and by two or four tracheae like those of insects. The air enters the compartments of the lung-books through an external slit flush with the skin. In the partitions between the compartments of the lung-books the blood circulates and is purified. Research Spider
Tick is a popular name applied vaguely to a large number of genera of Arachnida allied to the mites. Most of them are temporarily parasitic on animals, whose blood they suck by means of a rostrum or beak, swelling sometimes to several times their original size. In the tropics ticks are a serious pest, as they wait in ambush in homes, under stones and in foliage, waiting for an opportunity to attach themselves to any passing mammal, including man. Ticks convey many germs of diseases, such as relapsing or tick fever and spotted fever in man, Texas or redwater fever in cattle, and piroplasmosis in horses and dogs. The brown tick causes the so-called coast fever in cattle in South Africa. Research Tick
The whip-scorpion is a group of Arachnida of the order Pedipalpi, resembling the spider in having a narrow wait between the fore-part and the abdomen, but differing in having no silk glands. The second pair of limbs are modified as powerful grasping organs armed with spines for impaling their prey and the first pair of legs are turned into antenna-like feelers, resembling long whips in some kinds. Research Whip-scorpion
Abbreviations
Research Acarina
