lO 



sc/EycE-Goss/r. 



IXSTINXT. 



Bv K. Dickson-Bryso.n, B.A., I'.l'.S.. K.R.As.S. 



(Coitthttiai /rout V'oi. V., pa^e 305.) 



Is Spiders. 



npHE spinning faculty being that most inti- 

 ■'■ niately connected with the conception nf a 

 spider, it was easy and natural for the imaginative 

 Greeks to adopt it as their symbol for a woman. 

 Despite its evil reputation and false celebrity of 

 uijliness, we, who think of single ladies as 

 spinsters, naturally associate the spinder or spider 

 with them. Unfortunately for the reputation of 

 both spiders and women, we can never observe the 

 skill and art displayed in the construction of the 

 web, but we instinctively think of the purpose for 

 which they are employed. Spiders are not classed 

 with insects, from which they differ in having 

 simple eyes instead of compound, eight legs in 

 place of six, no antennae, anil not undergoing the 

 metamorphoses so characteristic of insect life. 

 Thev are distributed into two classes : Pulmo- 

 iiarla, or those which breathe by pulmonary cavi- 

 ties ; and Trac/ienria, or those that breathe by 

 trachea, like insects. They are classed according 

 to their habits, as Hunters. Wanderers. Sedenta- 

 ries, and Divers. 



The instinctive qualities are well-defined in the 

 spider family, and their study is an agreeable occu- 

 pation. The spider's web may be studied any- 

 where, but that of the garden spider (Epi:ira did- 

 'lima) is perhaps best known. The garden or 

 • liadem spider is easily recognised by the beautiful 

 white markings on its body, and by the dark bands 

 and spines on its legs. 



The web is an example of rare geometric skill, 

 and is made up of base lines radiating from a 

 common centre, with concentric polygonal spirals 

 winding to a distance of several inches from that 

 point. At the centre the spider takes its .■sentinel 

 post. Carefully examine the individual threads 

 with a lens and the concentric threads will be 

 found more glutinous than those radiating from 

 the centre. Place them under the microscope and 

 thousands upon thousands of globules will be 

 traced along its length. These globules constitute 

 |>C)ints of attachment, by which the concentric 

 threads are fixed to the radiating ones. A single 

 web of the garden spider has been foumi to contain 

 as many as 90,000 of these globules. The web of 

 the Eptira apotlUa, an allied species, usuallv 

 consists of twenty-six radiating lines, and twentv- 

 four rows of spirals. A large web has been esti- 

 mated to contain 120,000 globules. Besides the 

 radiating and spiral threads there are the base lines 

 extending beyond the outermost circle and fixed 

 like a cable to le.ives and branches, so as to 

 support the whole. 



A complete web, with its elaborate tracery of 

 radiating and circular lines and myriads of glo- 

 bules is produced in little less than forty-five 

 minutes. In this brief time the spider not only 

 arranges the warp and woof, with the utmost 

 mathematical precision, in their proper places, but 

 knits and s])ins the whole from its own body. 

 Carefully examining a single thread, we are at 

 once struck with its inconceivable tenuity. Any- 

 thing beyond a rouyh estimate of its actual 

 diameter is hopelessly outsiile our powers. The 

 thread is not, as we view it w'ith unassisted vision, 

 a single fibre, but is composed of strands, twisted 

 and spun together like a rope. A. rope, however, 

 is composed of only four or five strands, and here 

 the analogy fails. As many as four or five thou- 

 sand strands enter into a single spider's thread. 

 Some of these complex threads are so extremely 

 fine that 4,000,000 of them spun together would 

 scarcely equal in thickness an ordinary human 

 hair. Yet e.ach of these 4,000,000 threads is com- 

 ])osed of 4,000 others. The diameter of a single 

 strand is therefore the sixteen thousand millionth 

 ( ■6.0C0.L.000 ) P=»" of the thickness of a single 

 human hair. Such a statement seems reckless and 

 utterly beyond credibility, but the fact is one of the 

 many marvels abounding in lower forms of life. 



The spinneret is another marvel. This curious 

 mechanism is found on the lower posterior surface 

 of the s])ider's body. Careful inspection of this 

 part will reveal six small tube-shaped prominences. 

 On the apices of four of these prominences will 

 be found a number of minute openings — about a 

 thousand of each. Through each of these aper- 

 tures the spider ejects a fine viscid substance which 

 hardens on exposure to the air. These twisted to- 

 gether form one of the threads in the web. The 

 four tube-like prominences are called the spin- 

 neret. The remaining pair differ in structure and 

 function. Two kinds of thread are i>roduced by 

 the spinneret. The concentric threads possess a 

 viscidity not found in the radiating threads. The 

 incautious insect alighting on the trap is glued 

 down and held fast till the sjjider overpowers it in 

 its meshes. But whence does the s])ider procure 

 its material to spin? Behind the s])innerels arc 

 six or eight reservoirs, in which a glassy-looking 

 substance is formed and stored till rc(|uirc'' A 

 comb-like apparatus on the feet is used to spin, 

 card, and adjust the threads as they issue from the 

 pores of the spinneret. This example of animal 

 machinery exceeds in complexity anv of the devices 

 of man's ingenuity for a similar purpose. 



The mason spider, with an organisation almost 

 similar to that of the Epcira, has very ililferen; 



