394 INSECT TRANSFOKMATIONS. 



the spring in the tail, by means of which it leaps, 

 jerking it downwards and outwards from its body as 

 the flea does its legs. 



Leaping position of the velvet spring-tail, magnified. 



Amongst the insects which spring upon their prey 

 like the cat and the lion, the most commonly observed 

 is the little hunting -spider {Salticus scenicus), svhose 

 zebra stripes of white and brown render it easily dis- 

 covered on our window-frames and palings.* But 

 all the spiders — even those which form webs — are 

 accustomed to spring in a similar way upon what 

 they have caught; and when we are told of the 

 gigantic American one (JMygale avicularia)^ which 

 even makes prey of small birds (Trochilidce), the 

 necessity of extraordinary agility must be obvious ; 

 for these tiny birds are described to move with al- 

 most the velocity of light, — the eye, notwithstanding 

 the brilliancy of their metallic colours, being fre- 

 quently baffled in tracking their flight. The spider 

 itself, however, being three inches in length, one and 

 a half in breadth, and eleven inches in the expansion 

 of its legs, is little less than the bird upon which it 

 pounces, as may be seen from the following figure, 

 taken from the splended work of Madame Merian 

 upon the insects of Surinam. 



All animals which fly are furnished with powerful 

 muscles for moving their wings, in the same way as 

 the limbs of those which leap are similarly provided ; 

 * See Insect Architecture, p. 355. 



