. The biology of spiders. Spiders; Insects. EXTERNAL STRUCTURE 43 wherever they go. Four spigots, the two remaining on the median spinneret and two of the five on the posterior spinneret, are used only in the making of the cocoon. The coloured wadding often found protecting the eggs is taken from them. The three other spigots on each posterior spinneret produce not silk, but the glutinous fluid which makes the spiral thread of the web adhesive. Although deposited round the thread at the moment of formation it breaks up from the cylindrical to the more stable spherical form, and beads the line
. The biology of spiders. Spiders; Insects. EXTERNAL STRUCTURE 43 wherever they go. Four spigots, the two remaining on the median spinneret and two of the five on the posterior spinneret, are used only in the making of the cocoon. The coloured wadding often found protecting the eggs is taken from them. The three other spigots on each posterior spinneret produce not silk, but the glutinous fluid which makes the spiral thread of the web adhesive. Although deposited round the thread at the moment of formation it breaks up from the cylindrical to the more stable spherical form, and beads the line with a regular arrangement of minute globules. These differently functioning spigots are connected with different glands in the abdomen, which will be described in the next chapter. The cribellum (Fig. 28) is an oval plate found just in front of the anterior spinnerets in certain families of spiders, but not in all. It is perforated with a large number of minute pores, each of which is the orifice of the duct from a gland. These glands are found only in association with the cribellum itself, and are not represented by any analogue Fig. 28.—The Cribellum and Spinnerets of Amaurobius. in ecribellate families. The function of the organ is quite clear and may readily be witnessed in many common spiders. The activity of the glands secreting silk through numerous pores, produces a broad ribbon of silk composed of some hundreds of threads. This ribbon is combed out of the cribellum by the calamistrum on the fourth metatarsus The Cribellum. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Savory, Theodore Horace, 1896-. London : Sidgwick & Jackson
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecti, booksubjectspiders
