SPIDERS 



633 



No structures made by animals not even the 

 nests of birds, the homes of bees, the hills of the 

 Termites are more marvellous than the webs and 

 snares of spiders. The framework is so delicate 

 yet so effectively firm, so clever in its construction, 

 so sensitive, we may almost say, in its mechan- 

 ism, that we must rank it highest among works 

 of instinctive art. Instinctive, for each species of 

 weaver has its characteristic web, and there is no 

 reason to suppose that the art of making this is 

 the result of education. Yet the mode of construc- 

 tion is not rigidly fixed, but varies a little accord- 

 ing to the site, according to the wind, and even, it 

 is said, in relation to the abundance of insects in 

 the neighbourhood. We see the strength of the 

 wel> when it remains unbroken in the wind, and 

 when it is laden with drops of dew, but sometimes 

 it is much stronger than such sights suggest. 

 Mosely tells how Willemoes Suhm on the Chal- 

 lenger expedition found a Glossy Starling ( Calomis 

 metallica) hopelessly entangled in a spider's web, 

 and other naturalists relate the same of humming- 

 birds and other small creatures. Thus a snake, 

 nine inches long, has been found hanging in a web; 

 anil Dr McCook, whose carefulness as an observer 

 is worthy of all praise, relates how a young living 

 mouse was in some manner securely entangled in 

 the snare of a spider, how the spinner, by means of 

 silken threads two or three feet long, hoisted the 

 mouse up four inches, and how the mouse after 

 living for ten hours at length succumbed. A 

 spider three-quarters of an inch in length has been 

 seen to land a fish about three inches in length, 

 but perhaps the raising of a mouse in a web is 

 more wonderful. Mr Wallace and other exploring 

 naturalists also tell of spider-webs strong enough 

 to be a serious obstacle to travellers in the woods, 

 and in other reports fancy has magnified this 

 strength tenfold. As to the intelligence involved 

 in modifying the web in various conditions it is 

 not easy to form an accurate estimate. On a long 

 hedge we may see scores of webs disposed so as 

 best to stand the stress of the prevailing wind, but 

 we iini.-t remember that the foundation-lines of the 

 web are in most cases wind-blown. Often in the 

 geometric webs there are interesting irregularities 

 which show that equal precision is not always 

 attained. On the other hand fractured snares are 

 sometimes mended by skilfully disposed trusses. 

 Many observers have described cases where small 

 stones were found hung from the web, as if to 

 weight them against the force of the wind. But 

 McCook maintains, and we would agree with him, 

 that it is most likely that these stones have been 

 raised from off the ground by the shrinkage of the 

 web, and that the alleged advantage which, if 

 foreseen, involves a complex inference is simply 

 accidental. 



The threads which the spiders spin are used not 

 only in fashioning webs and snares, but in many 

 different ways. Behind them, as they move where 

 a footing is insecure, there trails a drag-line, per- 

 haps the rudiment of all their weaving, and this is 

 of special use when they drop from a height. 

 Jonathan Edwards long ago (1716) observed that 

 spiders in order to cross an unbridged gap will form 

 a sort of swinging basket, and he also noticed their 

 exceedingly strange habit of ballooning. Raising 

 themselves on tiptoe and with upturned abdomen 

 on some point of vantage, they allow long threads 

 of gossamer to float out in the air until these 

 acquire sufficient momentum to carry the spider 

 aloft. In this way they have been known to cross 

 considerable sheets of water. ' To this mode of 

 diversion young spiders of several families are very 

 much addicted, especially in the fine days of 

 autumn. Sometimes the flying threads are exces- 

 sively numerous, and on their descent cover every- 



thing; they are particularly striking on hedges, 

 and constitute, at all events, one of the causes of 

 the phenomenon well known in the country as 

 gossamer.' And again, the threads may help to 

 form the cocoon for the eggs, or may be used to 

 bind leaf to leaf and form a well-hidden nest. 



Enemies and Protective Adaptations. While 

 spiders are the fatal enemies of many insects, they 

 are in turn frequent victims. ' To feed the hungry 

 maw of a stronger, more skilful, or more fortunate 

 fellow Araneid ; to be paralysed and entombed 

 within a clay sarcophagus by a mother wasp, and 

 serve as food for a growing waspling worm (see 

 SPHEX ) ; to be snapped up as a delicate titbit by 

 birds, toads, and other creatures these are some 

 of the ways in which the spider meets its doom. ' 

 Among birds the chief enemies of spiders are the 

 humming-birds, among insects the wasps. The 

 ichneumon flies often lay their eggs with destruc- 

 tive results in the cocoons of spiders. Small 

 monkeys prey upon spiders a good deal, and! so do 

 some insectivorous mammals. Between different 

 kinds of hunting and running spiders there is much 

 keen warfare. 



Many spiders hide in crevices or in bivouacs 

 of leaves which they roll up or bind together. 

 McCook describes the nest of the Purse-web Spider 

 (Atmnis abbotii), a purse-shaped tube attached to 

 the bark of trees, with the outer surface dark and 

 covered with sand. The nests of the trap-door 

 spiders have lids which fit accurately, and are 

 covered with moss, earth, and lichen ; in fact the 

 nests of a great number of species believed to be 

 trap-door spiders have never been found. In many 

 cases the vibratory sensitiveness of the web is such 

 that an approaching enemy finds the spider fore- 

 warned. When Argiope cophinaria has not time to 

 drop from her web to the ground, ' she makes use 

 of another power she will render herself invisible. 

 The web begins to sway backward and forward ; 

 the rapidity of the motion increases ; the outlines 

 become indistinct, and within a few seconds of the 

 first movement spider, web, and all have vanished 

 from sight ! Others, such as Pholcus atlanticvs, 

 hang by the legs, and whirl the body rapidly with 

 the same bewildering result.' Mr Herbert Smith 

 suggests that the sideways movement of the 

 Laterigradiu has a protective value, since the 

 enemies are likely to allow for a forward movement 

 of their prey. Many Epeiridas and other spiders 

 drop to the ground when danger threatens, and 

 remain motionless on a surface which they often 

 resemble in colour. McCook seems inclined to 

 regard this death-feint as a trick, not as fear 

 paralysis or catalepsy. The cocoons are hidden in 

 crevices, or covered with web and debris, or carried 

 about by the mother sometimes attached to the 

 abdomen, sometimes in the jaws. For further 

 examples of the thousands of protective habits, 

 see the works of the Peckhams and Dr McCook. 



Often the forms and colours of spiders have a 

 protective resemblance to pieces of plants or to 

 dead things. The 

 species of Uloborus 

 are like small pieces 

 of bark ; Hyptioides 

 cavatus resembles a 

 bit of dirt or the 

 ends of the dead pine 

 branches among 

 which it lives ; 

 Cyrtophora cornea is 

 hardly distinguish- 

 able from the pieces 

 of light rubbish which it accumulates in its web ; 

 Ccerostris mitralis resembles a woody knot on the 

 branch on which it rests ; Thomisus foka, a species 

 much dreaded in Madagascar, has a very strange, 



Fig. 4. C&rostris mitralis on a 

 branch (after E. G. Peckham). 



