38 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



As many as one hundred and fifty or two hundred may be counted upon 

 the tip of a single spinneret of an Epeiroid spider, as for example, Ar- 

 giope cophiiiaria. These spinning spools are two jointed, at least they are 

 divided into two parts, of which the base is the thicker, 

 and sometimes the longer. They are hollow 

 .nnmg- i^^ through which the delicate ducts connected 

 with the silk glands convey the liquid silk to the 

 surface. These spinning spools are of several sizes and 

 shapes (Fig. 26), and differ somewhat according to their 

 position upon the several spinnerets. Thus those upon the 



FIGS. 27,28. View of r . . . 



a spinning spool anterior spinnerets have the basal part (bj) of a conical 

 *of of^eira'di" sna pe and rather shorter than the point or terminal joint, 

 ademata. (After tj. (Fig. 26 b, c, compare with Fig. 27.) 



Distributed here and there among these spools of ordi- 

 nary size are a few which are larger and stouter. (Fig. 28.) In Argiope 

 cophinaria there are three of these on each of the middle spinnerets, four 

 upon each of the posterior, and one upon each of the anterior ones. A 

 detailed description of these instruments will be given further on. 



These groups of spinning spools are surrounded by ranks of hairs and 



bristles (b, bb, br), both simple and branched, which are movable and 



appear to have some important part in spinning. Possibly they 



1 serve to direct the course of the threads as they issue from the 



spools, or it may be that they form a protection to the more 



delicately organized spinning spools themselves. 



II. 



The spinning spools are connected with a system of glands and ducts 

 constituting the internal spinning organs, the reservoir within which is 

 formed, and from which is secreted the material for all spinningwork. 

 When the integument of the lower and front 

 part of the abdomen is removed, to- 

 gether with the thin layer of fat and 



Internal 



Spinning- 



Organs muscles that move the spinner- 



ets, a large bunch of minute vesicles 

 visible to the naked eye in a large spider such 

 as Argiope cophinaria is brought into view. 

 Examined by the microscope they are found 

 to be small, transparent, oval sacs. These are 

 the silk glands. They are about one two-hun- 

 dredth of an inch in diameter, in Epeira di- 

 ademata (Meade) ; or 0.22 millimetre (Bucholz 

 and Landois). In Argiope cophinaria they are 

 of various lengths, averaging about (0.3 mm.) 

 three-tenths of a millimetre. 



py-g 



spn 



FIG. 29. View from beneath of the loca- 

 tion of spinning glands in Epeira di- 

 ademata. (After Meade.) spn, spin- 

 nerets ; py.g, pyriform, cy. g, cylindri- 

 cal, tr.g, treeform, glands. 



