INTRODUCTION. 
3 
in the species belonging to the genus Hersilia, which have the foot divided into three joints. 
The haunch, or coxa, is articulated with the cephalo-thorax. The first part of the thigh, or 
the exinguinal joint, is short, and is closely united to the haunch; the second part, or the 
femoral joint, being long. The first part of the shank, or the genual joint, is usually short, 
and is closely united to the second part, or the tibial joint, which is long. The parts of the 
foot are the upper or metatarsal joint, and the lower or tarsal joint, which latter is almost 
always terminated by two or more claws. Two of these claws, inserted one beside the other, 
are in general curved, and pectinated, and immediately below them another frequently occurs ; 
it is small, and abruptly inflected near the base, where a pair or two of minute teeth may 
sometimes be perceived. When the last claw is not present, a scopula or brush, consisting of 
coarse, compound, hair-like papillae, often occupies the inferior surface, or the extremity of the 
tarsi. Closely analogous to the tarsal cushions of insects in the function it performs, this 
apparatus enables its possessor to ascend hard dry bodies having highly polished, perpen¬ 
dicular surfaces, by the emission of a viscous secretion. 1 * 
In addition to the claws already described, some spiders have several small, dentated 
ones on the sides and lower part of the tarsi, at their extremity. This is the case with the 
Epeira in particular ; they have also a strong moveable spine, inserted near the termination of 
the tarsus of each posterior leg, on the under side, which curves a little upwards at its 
extremity, and exhibits a slight irregularity of outline at its superior surface. These spines, 
which have been denominated sustentacula, subserve an important purpose. By the con¬ 
traction of their flexor muscles they are drawn towards the foot, and are thus brought into 
immediate opposition to the claws, by which means the animals are enabled to hold with a 
firm grasp such lines as they have occasion to draw from the spinners with the feet of the 
hind legs, and such also as they design to attach themselves to. 3 
Like the palpi, the legs are provided in a greater or less degree with hairs and spines; 
and some spiders, Ciniflo atrox and Ergatis benigna, for example, have on the superior part of 
the metatarsal joint of each posterior leg two parallel rows of moveable spines forming a 
curling apparatus, employed in the construction of their snares. This apparatus has received 
the name of calamistrum? The relative length of the legs presents much diversity, and is not 
always alike even in the sexes of the same species. 
In much the greater number of spiders, the abdomen, attached to the cephalo-thorax by 
a short pedicle, is enveloped in a soft, continuous skin, covered more or less with hairs; but 
in some species its covering is of a hard, corneous consistency. The predominant forms of 
the abdomen are ovate, cylindrical, and subglobose, variously modified; and its figure is still 
further diversified in some species by fleshy tubercles and corneous spines. On its upper part 
or back it frequently exhibits divers colours, arranged according to numerous designs, which 
greatly contribute to the distinction of species. 
Placed immediately below the anus are the spinning-mammul®; they are four, six, or 
eight in number, conical or cylindrical in figure, composed of one or more joints each, and are 
1 ‘ Transactions of the Linnean Society/ vol. xvi, pp. 768, 769. ‘ Researches in Zoology/ p. 289. 
‘ Annals and Magazine of Natural History/ vol. xv, pp. 115-118. 
3 ‘ Transactions of the Linnean Society/ vol. xvi, p. 476 ; vol. xviii, p. 224, note. 
3 Ibid., vol. xvi, pp. 471-475 ; vol. xviii, pp. 224, 606. 
