Pedipalp are each of the second pair of appendages attached to the cephalothorax of most arachnids. Pedipalp are variously specialized as pincers, such as in scorpions, sensory organs, as is the case with spiders, or locomotory organs, as is the case with horseshoe crabs. Research Pedipalp
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
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Pedipalp
