Archive image from page 72 of American spiders and their spinning. American spiders and their spinning work. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits CUbiodiversity1121211-9742 Year: 1889 ( CONSTKUCTION OF AN ORBWKB. 73 It must be understood that I have only taken a case that may be con- sidered fairly typical of the general plan of construction. It will explain the ordinary principles and a common mode of proceeding; but in point of fact the details continually vary, according to the local pecul- Variable '' 'i ' te,
Archive image from page 72 of American spiders and their spinning. American spiders and their spinning work. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits CUbiodiversity1121211-9742 Year: 1889 ( CONSTKUCTION OF AN ORBWKB. 73 It must be understood that I have only taken a case that may be con- sidered fairly typical of the general plan of construction. It will explain the ordinary principles and a common mode of proceeding; but in point of fact the details continually vary, according to the local pecul- Variable '' 'i ' te, the conditions of the wind, and I suppose to some extent the individuality of the spider. Some incident will cause a variation; the advent of an insect, the presence of an enemy, the neighborhood of another \veb, a falling leaf, a fright or excitement of any sort may divert the spider's attention, and cause a variation in her plan. In short, her ' plan ' is to some extent elastic, and variable by the stress of accidents and circumstances; but as a general fact the exterior frame of the orb will be found to be a more or less regular quadrilateral or a triangle. Fig. 68. Double foundation lines. The foundation lines most commonly observed take the form of a trapezoid, whose sides are directly anchored to surrounding objects. Webs frequently occur, however, in which the orb with its trapezoidal Pounda- '''' hung within an outer foundation of strong cords usu- tions. Y' bt always, triangular in arrangement, as illustrated in Fig. 67. This form pi-evails in cases where the snare is hung within large open spaces, or stretched between two trees or bushes in woods. Some species appear to hang their snares quite habitually in this way, as with all the indigenous species of the genus Acrosoma whose industry is known to me. An example of this style of foundation is shown at Fig. 68, which is a snare of Acrosoma rugosa. Here we have two strong cords, ab, cd, united at J in a point, an
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