. 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. Spiders. THE SPINNING ORGANS. 39 They are placed in a mass just above the spinnerets, and within their bases and the abdomen, and along the venter forward and laterally. See Fig. 30. The pyriform glands, which are smaller and very much the most numerous, are arranged in five roundish clusters, about two millimetres in diameter in A. cophinaria, each corresponding to one of the exterior spin- nerets, one cluster being devoted to the two
. 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. Spiders. THE SPINNING ORGANS. 39 They are placed in a mass just above the spinnerets, and within their bases and the abdomen, and along the venter forward and laterally. See Fig. 30. The pyriform glands, which are smaller and very much the most numerous, are arranged in five roundish clusters, about two millimetres in diameter in A. cophinaria, each corresponding to one of the exterior spin- nerets, one cluster being devoted to the two middle spinnerets, al- though even in this case the clusters can be separated into two. The number of glands precisely corresponds with the number of spinning spools and spigots. Bucholz and Landois give about seven hundred for Epeira diademata and they are as numerous in Argiope cophinaria. Mr. Blackwall expresses the opinion that the total number of spinning spools does not greatly exceed a thousand, even in adult females of Epeira quadrata, whose weight is about twenty grains, and in many other species it is smaller. As the spools correspond in number with the glands, this gives an indication of the number of silk glands within our best known Silk Glands: Fig. 30. Partly diagramatic view of the location of the spinning organs in Argiope cophinaria. spn, spinnerets; , pyriform glands; , cylindrical glands; , treeform glands; ep, epigynum; gl, gills: E, eggs; , alimentary canal; a, anus. Th figure is a composite one. Orbweavers. Each gland terminates in a long, delicate duct, and one duct enters one of the spools; a distinct duct belongs to every spool, without any connection, as a rule, with other ducts or glands. Under the microscope the liquid silk can be seen very distinctly within the glands, and presents the appearance of minute, yellowish, translucent glob- ules of thickish oily or viscous substance. Some of the glands of Argiope cophinaria appe
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectspiders, bookyear1889
