454 



ARACHNIDA. 



THE FIRST FAMILY OF THE PULMONARY ARACHNIDA,— 



The Fileuses or Araneides, — 



Consists of the genus of Spiders, Aranea, Linn., in which the palpi resemble small feet without a claw 

 at the tip, terminated at most in the females by a small hook, and of which the terminal joint incloses 

 or supports, in the males, various appendages, more or less complicated, employed in generation.* The 

 frontal claws (mandibles of authors) are terminated by a moveable hook, which folds downwards, having 

 on its under side, near its pointed extremity, a small slit for the emission of venomous fluid secreted 

 in a gland of the preceding joint. The maxillse are never more than two in number ; the tongue is of 

 a single piece, always external, and situated between the inaxillas, and more or less square, triangular, 

 or semicircular. The thorax f has generally a V-like impression, indicating the region of the head, 

 but consists of a single piece, to which is posteriorly attached, by means of a short peduncle, a moveable 

 and generally soft abdomen. This part of the body is furnished in all the species beneath the anus 

 with four or six nipples, fleshy at the tips, cylindrical or conical, articulated, closely approximating 

 together, and pierced at the extremity with an infinity of minute orifices J for the discharge of silken 

 threads of an extreme tenuity, emitted from internal reservoirs. The legs, identical in form, but dif- 

 ferent in length, are composed of seven joints, of which the first two form the haunch, the next the 

 femur, the fourth § and the fifth the tibia;, and the two others the tarsus. The last is ordinarily ter- 

 minated by two ungues, generally toothed beneath, and by a third smaller unguis, not toothed. The 

 intestinal canal is straight ; the first stomach is composed of several sacs, and about the middle of the 

 abdomen is a second stomach-like dilatation. 



The nervous system is composed of a double chord, occupying the mid-line of the body, and of 

 ganglions, which distribute nerves to the various organs. According to Treviranus, the number of 

 ganglions is only two. The upper surface of the abdomen exhibits, especially in the smooth, naked 

 species, various impressed spots, differing in number and situation, which, according to Dufour, are 

 produced by the attachment of the filiform muscles which traverse the liver. The pulmonary orifices, 

 two or four in number, are indicated externally by as many yellowish or whitish spots near the base 

 of the belly, immediately after the segment, which, by means of a fleshy filament, unites the abdomen 

 with the thorax. Each pulmonary mass is formed by the superposition of a great number of white, 

 triangular, extremely slender plates, which become confluent around the spiracles, of which the num- 

 ber is the same as that of the pulmonary sacs. The female Araneides have two ovaries, quite distinct, 

 lodged in a kind of capsule formed by the liver. With respect to the simple eyes, Dufour observes, 

 that they shine in the dark like those of the Cat, and that in effect the Araneides can see both by day 

 and night. The abdomen of Spiders is subject to so great an alteration after death that its colours 

 and even its form are not recognizable. Dufour has, however, been enabled, by means of very rapid 

 desiccation (of which he has given the process), to remedy this evil in a great degree. 



According to Reaumur, the silk undergoes a first elaboration in two small reservoirs, like drops of 

 glass, placed obliquely, one on each side, at the base of six other reservoirs, like intestines, situated at 

 the side of each other, and folded up six or seven times, and proceeding to the nipples by a very 

 slender filament. It is in these latter vessels that the silk acquires greater strength, and other pro- 

 perties which it possesses. On leaving the nipples the silken threads are glutinous ; they require a 

 certain degree of desiccation or evaporation of humidity to fit them for use. But it appears that in 

 favourable weather a moment is sufficient, the animals making use of their threads as soon as they are 

 discharged. The white, silky masses seen floating in the air in spring and autumn, called in France 

 fils de la vierge, are certainly produced, as we have proved, by tracing them from their point of de- 

 parture, from various young Spiders, especially Thomisi and Epeirse. It is also probable that many of 



* After all the observations which have been made upon the coupling 

 of spiders, I am induced to believe these appendages are organs of 

 generation. I have in vain sought for any ventral organs, in a large 

 male Mygale, preserved in spirits. We ought not always to decide 

 upon analogy — for instance, the female organs of Glomeris and Jnlus 

 are situated near the mouth— a fact of which there is no second 

 example. 



t The expression cephalothorax would be more correct, but it is 

 not in common use. Neither do I use the term corselet, which is 



generally used, because it is ordinarily also applied to a portion only 

 of the thorax, namely, the prothorax, in Coleopterous and Orthoptcrous 

 insects. 



X These orifices are upon the terminal joint, which is often with- 

 drawn. If pressed sharply, a number of minute papillje, pierced at the 

 tip (which are the real spinuertts), are protruded. Some naturalists 

 are of opinion that the two small nipples placed on the middle of the 

 four others do not supply silken threads. 



§ This joint, the first of the tibia, is a kind of rotule. 



