MOTIONS OF INSECTS. 



253 



the rest Anthrophora spumaria, have the extremity of the 

 above tibiae armed with a coronet of spines; these are of great 

 use in pushing them off when the legs are unbended. This 

 insect, when about to leap, places its posterior thighs in a di- 

 rection perpendicular to the plane of position, keeping them 

 close to the body ; it next with great violence pushes them 

 out backwards, so as to stretch the leg in a right line. These 

 spines then lay hold of the surface, and by their pressure 

 enable the body to spring forwards, when, being assisted by 

 its wings, it will make astonishing leaps, sometimes as much 

 as five or six feet, which is more than 250 times its own 

 length ; or as if a man of ordinary stature should be able at 

 once to vault through the air to the distance of a quarter of a 

 mile. Upon glass, where the spines are of no use, the insect 

 cannot leap more than six inches. 1 The species of another 

 genus of the homopterous Hemiptera (Chermes), that jump 

 very nimbly by pushing out their shanks, are perhaps assisted 

 in this motion by a remarkable horn looking towards the anus, 

 which arms their posterior hip. Some bugs that leap well, 

 Acanthia saltatoria, &c, seem to have no particular apparatus 

 to assist them, except that their posterior tibiae are very long. 

 Several of the minute ichneumons also jump with great agility, 

 but by what means I am unable to say. There is a tribe of 

 spiders, not spinners, that leap even sideways upon their prey. 

 One of these ( Salticus scenicus), when about to do this, elevates 

 itself upon its legs, and lifting its head seems to survey the 

 spot before it jumps. When these insects spy a small gnat or 

 fly upon a wall, they creep very gently towards it with short 

 steps, till they come within a convenient distance, when they 

 spring upon it suddenly like a tiger. Bartram observed one 

 of these spiders that jumped two feet upon a humble-bee. The 

 most amusing account, however, of the motions of these 

 animals is given by the celebrated Evelyn in his Travels. 

 When at Rome, he often observed a spider of this kind hunt- 

 ing the flies which alighted upon a rail on which was its sta- 

 tion. It kept crawling under the rail till it arrived at the part 

 opposite to the fly, when stealing up it would attempt to leap 



1 De Geev, iii. 178. 



