38 



AMERICAN SPIDERS AND THEIR SPINNINGWOKK. 



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- 

 gioi)0 cophinaria. 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 

 j;^ , tubes, tlirougli which the delicate ducts connected 

 witli the silk glands convey the litjuid silk to tlie 

 surface. These spinning spools are of several sizes and 

 sliaj^es (Fig. 26), and differ somewhat according to their 

 position upon the several spinnerets. Thus those upon the 

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

 shape and rather shorter than the point or terminal joint, 

 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 tliere 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 tliese instruments will be given further on. 



These groups of spinning sjjooIs 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. Possiljly they 

 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 siiinning spools themselves. 



sp 



Figs. 27, 28. View of 

 a spinning spool 

 and spinning spi- 

 got of Epeira di- 

 ademata. (After 

 Meckel.) 



Hairs and 

 Bristles. 



Internal 



Spinning 



Organs. 



II- 



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

 constituting the internal spinning organs, the reservoir within wliich 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 

 the muscles that move the si)inner- 

 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 fouiul 

 to be small, transparent, oval sacs. These arc 

 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 



. T « ''''"■ ^^' View from beneath of the loca- 



and Landois). In Argiope cojihinaria they are tion of spinning glands in Epeira di- 

 of various lengths, averaging about (0.3 mm.) edemata. (After Meade.t spn spin- 



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



three-tenths of a millimetre. cai, tr,g, treeform, glands. 



