SILK SPINNING AND HANDIWORK 53 



having reference to women who spin as a profession, but the latter 

 has acquired a quite different connotation. 



While most people associate spiders with a silken web of some 

 sort, few are aware of the dependence of these creatures on silk. 

 The ability to spin is an early gift to the spiderling, and is developed 

 after the first molt and before emergence from the egg sac. Imme- 

 diately upon leaving the sac, the spiderling strings out its dragline 

 threads and attaches them at intervals to the substratum. There- 

 after it is never free of this securing band through its whole life, 

 except by an accidental breaking of the cord. 



The degree of reliance on silk varies considerably among the 

 spiders. The very oldest ones, the precursors of those few we 

 know from Carboniferous rocks, probably had clumsy appendages 

 that were only beginning to be used to comb out a liquid silk. The 

 most primitive of recent spiders are said not to spin a dragline, 

 although they are otherwise probably as well equipped for spin- 

 ning as most spiders, from the evidence of their well-made egg sacs 

 and silken tubes closed with a trap door. The familiar jumping 

 spiders and wolf spiders, so often seen running over the ground or 

 climbing on plants, are vagrant types in which the use of silk is lim- 

 ited. They employ it chiefly for their draglines, for covering their 

 eggs, and for lining their retreats. On the other hand, a vast multi- 

 tude of sedentary spiders are strongly dependent on silk. Some of 

 them have become slaves of elaborate webs and are nearly helpless 

 when not in contact with them. For spiders of this type silk is of 

 paramount importance during the whole life span. 



The majority of spiders are inveterate spinners and far surpass 

 all other animals in the variety and excellence of their weaving. 

 Some of the other arachnids produce silk, but they use it in a very 

 limited way. The pseudoscorpions have cephalic glands and spin 

 silk through a tiny spinneret located on the tip of the movable fin- 

 ger of the chelicera. Before laying their eggs, these tiny animals 

 build an ingenious little domicile made of small particles cemented 

 together with silk, and lined inside by a covering of silk. A few of 

 the mites also have silk glands and are said to spin threads so fine 

 they are invisible to the naked eye. The so-called "red spiders" are 

 mites of the family Tetranychidae, which cover the leaves of trees 

 with silk and use it as a protecting blanket for their eggs and young. 



Many insects spin silk and in such profusion that they rival the 

 work of even the sedentary spiders. The unsightly webs of the 

 tent caterpillars are familiar and despised objects to most people but, 



