The Structure and Habits of Spiders E-Book

J. H. Emerton

• Herausgeber: Books on Demand
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 67

Veröffentlichungsjahr: 2018

Beschreibung

The object of this book is to give a plain account of the best known habits of spiders, and as much of their anatomy and classification as is necessary to understand these habits. The portion on the spinning and flying habits is copied chiefly from Blackwall and Menge; that on the trap-door spiders from Moggridge; and the habits of Nephila and Hyptiotes, from Wilder. The observations of these authors have been repeated as far as possible, and some changes and additions made to their accounts of them. The numerous stories of deadly poison, supernatural wisdom, and enormous size and strength of spiders, have been omitted as doubtful. Several cuts from the papers of Professor Wilder have been repeated by favor of the author and publishers. Most of the figures are, however, new, and engraved by photography from my own drawings.

Leseprobe

The Structure and Habits of Spiders

The Structure and Habits of SpidersPREFACE.CHAPTER I.ANATOMY AND CLASSIFICATION.CHAPTER II.EATING AND BITING.CHAPTER III.SPINNING HABITS.CHAPTER IV.GROWTH OF SPIDERS.BOOKS ABOUT SPIDERS.Copyright

The Structure and Habits of Spiders

J. H. Emerton

PREFACE.

The object of this book is to give a plain account of the best known habits of spiders, and as much of their anatomy and classification as is necessary to understand these habits. The portion on the spinning and flying habits is copied chiefly from Blackwall and Menge; that on the trap-door spiders from Moggridge; and the habits of Nephila and Hyptiotes, from Wilder. The observations of these authors have been repeated as far as possible, and some changes and additions made to their accounts of them. The numerous stories of deadly poison, supernatural wisdom, and enormous size and strength of spiders, have been omitted as doubtful. Several cuts from the papers of Professor Wilder have been repeated by favor of the author and publishers. Most of the figures are, however, new, and engraved by photography from my own drawings.

CHAPTER I.ANATOMY AND CLASSIFICATION.

The spiders form a small and distinct group of animals, related to the scorpions, the daddy-long-legs, and the mites, and less closely to the insects and crabs. They are distinguished by the more complete separation of the body into two parts; by their two-jointed mandibles, discharging a poisonous secretion at the tip; and by their spinning-organs, and habits of making cobwebs and silk cocoons for their eggs.

The common round-web spider,Epeira vulgarisof Hentz, will serve as well as any species to show the anatomy of spiders in general.Fig. 1shows the under side of this spider;Fig. 4, the upper side; andFig. 5, an imaginary section through the body, to show the arrangement of the internal organs. To begin withFig. 1: the body is seen to be divided into two parts, connected only by the narrow joint, A, just behind the last pair of legs. The front half of the body, called the thorax, contains the stomach, the central part of the nervous system, and the large muscles which work the legs and jaws. The hinder half, the abdomen, contains the intestine, the breathing-organs, the principal circulating-vessels, the organs of reproduction, and the spinning-organs. Connected with the thorax are six pairs of limbs, four pairs of legs, B B B B, a pair of palpi, C, and a pair of mandibles, D.

Fig. 1.

LEGS.

The legs are used chiefly for running, jumping, and climbing; but the front pair serve often as feelers, being held up before the body while the spider walks steadily enough on the other six. One or both of the hinder legs are used to guide the thread in spinning; the spider at the same time walking or climbing about with the other six or seven. The legs are seven-jointed; and on the terminal joint are three claws,Fig. 2, A, B, C, and various hair and spines. In many spiders a brush of hairs takes the place of the middle claw, as in the jumping spiders,Fig. 3. Spiders with these brushes on their feet can walk up a steep surface, or under a horizontal one, better than those who have three claws. The legs of most spiders have among the hairs movable spines, which, when the spider is running about, extend outward at a right angle with the leg, and, when it is resting, are closed down against the skin.

Fig. 2.

PALPI.

In front of the legs are the palpi,Fig. 1, C, C,—a smaller pair of limbs, with six joints and only one claw or none. They are used as feelers, and for handling food, and, in the males, carry the curious palpal organs, which will be described farther on. The basal joints,Fig. 1, E, of the palpi are flattened out, and serve as chewing-organs, called “maxillæ.”

Fig. 3.

Mr. Mason has lately described, in the Transactions of the Entomological Society of London, a large spider which has teeth on the inside of the palpi, which, when the spider is angry, are rubbed against teeth on the mandibles, producing a noise.

MANDIBLES.

The front pair of limbs, the mandibles,Fig. 1, D, are two-jointed. The basal joint is usually short and stout, and furnished on the inner side with teeth and hairs. The terminal joint is a small and sharp claw, which can be closed against the basal joint when not in use.

ABDOMEN.

On the under side of the abdomen, just behind the last pair of legs, are two hard, smooth patches, which cover the front pair of breathing-organs, the openings to which are two little slits atFig. 1, H. Between these is the opening of the reproductive organs, and, in female spiders, the epigynum,Fig. 1, J,—an apparatus for holding the reproductive cells of the male.

At the end of the body are the spinnerets, which will be described in another chapter. There are three pairs of them; but many spiders close them together when not in use, so as to cover up the middle pair. The third pair of spinnerets are often several-jointed, and extend out behind the body like two tails. In front of the spinnerets is a little opening,Fig. 1, K, which leads to air-tubes that give off branches to different parts of the abdomen. At M,Fig. 1, are usually two colored bands, or rows of spots, marking the course of muscles attached to the skin at various points along these lines.

Fig. 4is the back of the same spider. The head is not separated from the rest of the body, as in insects, but forms, with the thorax, one piece. On the front of the head are eight eyes, Q, which are differently arranged in different spiders. At the back part of the thorax is a groove, P, under which is attached a muscle for moving the sucking-stomach,Fig. 5,d. From this point radiate shallow grooves, that follow the divisions between the muscles of the legs. On the abdomen are several pairs of dark smooth spots, which mark the ends of muscles extending downward through the abdomen. The markings of this spider are very complicated. The spot on the middle of the front of the abdomen is a very common one, and, in some spiders, extends the whole length of the body. The waved lines on each side are also common, and, in long-bodied spiders, often form two bright-colored stripes, or rows of spots, running nearly straight the whole length of the abdomen.

Fig. 4.

INTESTINE.

Fig. 5is a section of the same spider. The mouth is ata b, just under and behind the mandibles, and between the maxillæ. It has an upper,a, and under lip,b, each lined with a horny plate, in the middle of which runs a groove. When the lips are closed, the two grooves form a tube, which leads to the œsophagus,c, and so into the stomach. At the end of the œsophagus is the sucking-stomach. This consists of a flattened tube, to the top of which is attached a muscle,d, connected with the groove in the back; and to the bottom, muscles,f, attached to a tough diaphragm spreading across the thorax, and fastened between the legs on each side atg g. When these muscles contract, the top and bottom of the sucking-stomach are drawn apart, and whatever is in the œsophagus sucked in. By this pumping motion the spider is supposed to take liquid food from the mouth, and drive it backward into the abdomen. Just behind the sucking-stomach, the intestine gives off two branches,e e, which extend forward around the stomach muscle, and meet over the mouth. Each of these branches gives off on the outer side four smaller branches,m m m m, which extend downward,—one in front of each leg,—and unite on the under side of the thorax.

Fig. 5.

Section of a spider to show the arrangement of the internal organs:

a,b, upper and under lips of the mouth;c,c, the œsophagus;

d,f, upper and under muscles of the sucking-stomach;

e, stomach;g,g, ligaments attached to diaphragm under the stomach;

J, lower nervous ganglion;k, upper ganglion;

l,l, nerves to the legs and palpi;m, branches of the stomach;

n, poison-gland;o, intestine;p, heart;R, air-sac;

S, ovary;t, air-tube;u, spinning-glands.

The intestine,o, continues backward through the abdomen to the anus, in the little knob behind the spinnerete. The brown mass which surrounds the intestine, and fills the abdomen above it, is supposed to be a secreting-organ discharging into the intestine at several points.

HEART.

Over the intestine, and parallel with it, is the heart,p, a muscular tube, with openings along the sides to receive the blood, and branches through which it flows to different parts of the body. The greater part of the blood enters at the front of the heart, and passes backward into the abdomen, or forward into the thorax.

BREATHING-ORGANS.