164 SPIDERS 



horizontal beam, it is able to maintain its position by means of an 

 adhesive tuft of hairs, the 'scopula', on each of its feet. As it moves, 

 the zebra spider trails behind it an exceedingly fine thread of silk 

 which is attached at frequent intervals like a climbing rope, so that 

 in the event of a slip the spider does not fall to the ground. The 

 species has a curious way of exploring the surface over which it is 

 working by successive short runs alternating with periods of 

 absolute stillness. It will often patiently search a large area before 

 it catches sight of an insect, when it can be seen to turn its head so 

 as to bring its four large anterior eyes to bear upon the quarry. The 

 four posterior eyes are smaller and less important. For a time it 

 remains motionless, then begins to edge stealthily nearer until it is 

 close enough for a sudden spring. The front pair of legs is used for 

 seizing the prey and the remaining pairs for jumping. However, 

 the jump is not always successful: often the insect sees its peril at 

 the last moment and flies away, and the spider has to begin all over 

 again. In contrast, the wolf spiders (Lycosidae) capture their 

 prey by sheer strength and speed. 



The typical crab spiders (Thomisidae) are seldom seen by the 

 ordinary observer, for their habits are retiring and many of them 

 are rather small. They wait motionless for passing insects which 

 are seized by the powerful outstretched legs, and having buried 

 their jaws in the head or thorax of the prey, they draw their limbs 

 backwards out of danger of the victim's bite or sting. Some species 

 however are true rovers hunting by day and passing the night 

 wherever they happen to find themselves. Those that lie in wait 

 often show a remarkable degree of resemblance to the colour of 

 their background. One East Indian species spins a white patch of 

 silk on the upper surface of a leaf. Lying on this, it looks exactly 

 like the dropping of some bird, and such droppings seem to be 

 particularly attractive to butterflies! No doubt, however, predation 

 by birds has been an even more important factor in natural 

 selection. The Oxyopidae, sometimes called lynx spiders, are 

 handsome hunting spiders that have become specialised for life on 

 plants. They can run over vegetation with great agility and leap 

 from stem to stem with a precision surpassed only by that of true 

 jumping spiders. The only British example of this family is the 

 rare Oxyopes heterophthalmus. 



