Page:The American Cyclopædia (1879) Volume XV.djvu/276

 SPIDER the legs and palpi; the intestine arises from uuular stomach, traverses the abdomen on the median line, and before ending at the anus forms a cloacal dilatation ; salivary glands exist in a cavity above the palate, communi- cating with the mouth by a slit in the upper lip ; the liver is very large, enveloping most of the viscera, of a dirty yellow, made up of nu- merous branches and closely aggregated casca, opening into the middle portion of the intes- tine. The blood is colorless; there is a heart, dorsal vessel with many constrictions, arteries, and vessels returning the blood from the respi- ratory organs. Respiration takes place both by pulmonary sacs and tracheae, one or the other penetrating all parts of the body and limbs ; there are two sacs occupying the base of the abdomen, containing more or less la- mellro ; the blood penetrates to the respiratory system probably by a kind of infiltration. Distinct urinary organs are present, much ramified glandular tubes pouring a whitish or reddish secretion into the cloaca. There are two poison glands at the base of the cheli- ceres, communicating with their terminal hook. The apparatus which secretes the viscid trans- parent liquid, hardening into silk on expo- sure to the air, consists of glandular follicles and tubes, of various forms and arrangement, in the midst of the abdominal organs ; in most spiders there are three pairs (in some two) of jointed spinnerets or obtusely conical papilla3 behind the anus ; the apex of these papillae is surrounded by stiff bristles and hairs, and is dotted with numerous horny tubes, the prolongation of the excretory ducts; the number of the tubes varies from 1,000 in epelra to less than 100 in the smaller spe- cies. The sexes are separate, and the eggs are numerous and spheroidal ; a single impreg- nation is sufficient for several successive gen- erations. There is generally only one brood in a year; the embryos are developed after the deposition of the eggs, and are hatched some- times in a few weeks, and at others not till the following spring ; the eggs are enveloped in a silken bag, from which the young are some- times helped out by the mother ; they resemble the parents except in size, and undergo no metamorphosis but change of skin ; life may be prolonged for several years. Only the system of classification of YValckenaer will be briefly given here, as it places stress on the most in- teresting points in their economy, though not affording a sufficient basis for natural classifica- tion. He divides the spinning spiders into ter- restrial and aquatic, as follows: I. Venantes, always running or leaping near their abode in search of prey, with the families : 1, latebrico- la, hiding in holes and fissures, like my gale ; 2, tubicola, enclosing themselves in silken tubes (dytdera, *egetria)', 3, cellulicola, living in small cells (scytodes) ; 4, cursores, swift runners (lycosa, ctenus); 5, saltatores, leaping with agility (attufi). II. Vagantes, wandering after prey, without fixed residence except while lay- ing eggs, with family 6, laterigradce, walking and running sideways or backward, and occa- sionally throwing out threads to entrap their prey (thomisus). III. Errantes, prowling in the neighborhood of their nests or threads, with families : 7, niditelce, going abroad, but making a web whence issue threads to entrap prey (clubiona, drassus) ; 8, filitelce, spreading long threads about their prowling places (phol- cws, eloiho). IV. Sedentes, spinning large webs and lying in wait in the middle or at the side, with families : 9, tapitelce, spinning large webs of close texture in which they dwell (tegenaria, agelena)-, 10, orlitelai, spreading orbicular or spiral webs of a regular open texture, living in the middle or at the side {epelra} ; 11, retitelce, spinning irregular webs of open meshes, re- maining in the middle or on the side (theridiori). V. Natantes, swimmers, spreading filaments in water, with family: 12, aquitelce (argyroneta). Spiders are found in every habitable portion of the globe, but are largest in warm climates; the males and females live separately, and the latter are most frequently seen and are consid- erably the larger ; all are carnivorous, devour- ing living prey, sucking the juices and some- times swallowing the fragments ; the females are generally ready to attack and feed on the males, even in the reproducing season, and both sexes are fond of fighting, the vanquished being devoured ; they can support long fasts, and remain torpid during the winter ; they are very cleanly, and spend much time in clearing their limbs from dust and dirt by the toothed combs and brushes on the mandibles. In ma- king their webs they accommodate themselves remarkably to circumstances, displaying great perseverance, ingenuity, and almost intelli- gence ; they carefully guard their eggs, some- times carrying about with them the silken bag which contains them, and are affectionate to their young, which in some cases devour their mother. They descend by their silken threads head downward, but climb up on them head upward, rolling them into a bundle during the ascent; the thread cannot be used a second time for the same purpose. "When they wish to go from tree to tree, some let go a thread in the direction of the wind, and when it has reached the object they strengthen and pass over it, in this way travelling long distances without de- scending to the ground ; their tiny cables are very abundantly seen in dewy mornings of spring and autumn ; some small gossamer spi- ders even speed through the air buoyed up by their light threads. They are capable of some domestication ; Pelisson, a prisoner in the Bas- tile, had a pet spider which came regularly, at the sound of a musical instrument, to get its meal of flies ; and a spider raiser in France is said to have tamed 800, which he kept in a sin- gle apartment for their silk. The supply of the silk of the spider seems to be limited to suffi- cient to make six or seven webs in a season ; it is very strong and very fine, and is used in astron- omy for the divisions of the micrometer ; ac-