SPIDERS' SILK. 



like. Among other even more important differences, 

 they have four pairs of legs ; also the head and thorax are 

 merged in one piece (cephalothorax). A pair of palpi 

 are frequently so developed as to look like a fifth pair of 

 legs. The eyes are simple, usually eight in number, and 

 differing in size and arrangement in different sorts of 

 spiders. The bite of all spiders is poisonous that is the 

 way they kill their food but there is so little poison and so 

 few spiders are strong enough to bite through the human 

 skin, even if they would try, that spiders are not danger- 

 ous. At the hind end of the abdomen are small appen- 

 dages, the spinnerets, from which come fluids that harden 

 on exposure to air and form silk. The silk of insects comes 

 from their mouths. 



Its uses by spiders, I mean, although it 

 Spiders silk . 



and its Uses ^ as been used by man for cross-threads in 

 telescopes and makes a better quality of 

 textile than the silk of moths. One sufficient reason 

 for man's not using it in the latter way is the difficulty 

 of getting enough of it. Spiders originally used silk 

 only to wrap up their masses of eggs (see Lycosa, Plate 

 VII). Then they took to lining their retreats with 

 silk; later they built platforms outside of their retreats 

 and from these developed the snares which have been the 

 wonder and admiration of all ages, humanly speaking. 

 These snares, even those which are orb-shaped, differ 

 greatly among themselves. Most of the orb-snares are 

 made by members of a single family, Argiopidae (or 

 Epeiridae), and a large proportion of our spiders make 

 no snare, catching their prey by stealth, fleetness of 

 foot or length of jump. Silk is used by certain young 

 spiders for "ballooning"; they stand on some elevation, 

 spin a thread into the air and, when the wind catches 

 it, sail away. This is the explanation of "showers of 

 gossamer." 



This is not the place to go minutely into 



The Kinds of . .. ,..,., 



Spiders the subject, but spiders may be divided 



into two sorts: what are called, in this 

 country, tarantulas and the, strictly speaking, spiders. 



3 33 



