10 
INTRODUCTION. 
formed of a compact, horizontal sheet of web, with a tube of greater or less dimensions at or 
near one of its margins, from which several lines frequently extend along its upper surface to 
the other margins, where they become attached. A fourth presents the appearance of an 
irregular web of white or bluish silk, the tortuous filaments of which have been curled and 
inflected by the calamistra before described ; in this snare one or two funnel-shaped tubes 
usually occur. The most elegant snares, however, are those constructed with the appearance 
of geometrical precision in the form of circular nets. They are composed of an elastic spiral 
line, thickly studded with minute globules of liquid gum, whose circumvolutions, falling within 
the same plane, are crossed by radii converging towards a common centre, which is imme¬ 
diately surrounded by several circumvolutions of a short, spiral line, devoid of viscid globules, 
forming a station from which the toils may be superintended by their owner without the 
inconvenience of being entangled in them. As the radii are unadhesive, and possess only a 
moderate share of elasticity, they must consist of a different material from that of the viscid, 
spiral line, which is^elastic in an extraordinary degree. Now, the viscidity of this line may be 
shown to depend entirely upon the globules Avith which it is studded, for if they be removed 
by careful applications of the finger, a fine, glossy filament remains, which is highly elastic, 
but perfectly unadhesive. As the globules, therefore, and the line on which they are disposed, 
differ so essentially from each other and from the radii, it is reasonable to infer that the 
physical constitution of these several portions of the net must be dissimilar. 
An estimate of the number of viscid globules distributed on the elastic, spiral line in a 
net of Epeira apoclisa of a medium size, will convey some idea of the elaborate operations 
performed by the Epeirce in the construction of their snares. The mean distance between two 
adjacent radii, in a net of this species, is about seven tenths of an inch; if, therefore, the 
number seven be multiplied by twenty, the mean number of viscid globules which occur on 
one tenth of an inch of the elastic spiral line, at the ordinary degree of tension, the product will 
be 140, the mean number of globules deposited on seven tenths of an inch of the elastic, 
spiral line; this product multiplied by twenty-four, the mean number of circumvolutions 
described by the elastic spiral line, gives 3360, the mean number of globules contained 
between two radii ; which, multiplied by twenty-six, the mean number of radii, produces 87,360’ 
the total number of viscid globules in a finished net of average dimensions. A large net, 
fourteen or sixteen inches in diameter, will be found, by a similar calculation, to contain 
upwards of 120,000 viscid globules, and yet Epeira apoclisa will complete its snare in about 
forty minutes if it meet with no interruption. 1 
In the formation of their snares the Epeirce appear to be regulated solely by the sense of 
touch, as various species, when confined in spacious glass jars placed in situations absolutely 
impervious to light, construct nets which do not exhibit the slightest irregularity of plan or defect 
of structure. 
Dr. Lister supposed that spiders are able to retract the lines they spin within the 
abdomen, and whoever minutely observes the Epeirce, when fabricating their snares, will almost 
be induced to entertain the same opinion. The viscid line produced by these spiders in their 
transit from one radius to another, is sometimes drawn out to a much greater extent than is 
necessary to connect the two, yet on approaching the point at which it is to be attached, it 
1 ‘ Transactions of the Linnean Society,’ vol. xvi, pp. 477-479. 
