Snares of another type consisting of a tangled mass of threads amongst which the spiders pick their way with ease, but which are impassable to insects, are spun by members of the Theridiidae and Pholcidae; but by common consent the so-called orbicular web, so characteristic of the Argyopidae but by no means confined to them, is regarded as manifesting the greatest perfection of instinct in snare-spinning.
Perfect orbicular webs are made by many genera of Argyopidae (Zilla, Meta, Gasteracantha), the best-known example being that of the common garden spider of England, Aranea or Epeira diademata; but these webs are not associated with any tubular retreat except such as are made under an adjoining leaf or in some nook hard by.
Limopsidae.-Shell orbicular, hinge curved, ligament longer transversely than antero-posteriorly; foot elongate, pointed anteriorly and posteriorly.
Amussiidae.-Shell orbicular, smooth externally with radiating costae internally.
The form of the leaf shows a very great variety ranging from the narrow linear form with parallel sides, as in grasses or the needle-like leaves of pines and firs to more or less rounded or orbicular - descriptions of these will be found in works on descriptive botany - FIG.