MOTIONS OF INSECTS. 317 



often observed a spider of this kind hunting the flies 

 which alighted upon a rail on which was its station. 

 It kept crawling under the rail till it arrived at the 

 part opposite to the fly, when stealing up it would at- 

 tempt to leap upon it. If it discovered that it was not 

 perfectly opposite, it would immediately slide down 

 again unobserved, and at the next attempt would come 

 directly upon the fly's back. Did the fly happen not to 

 be within a leap, it would move towards it so softly, 

 that its motion seemed not more perceptible than that 

 of the shadow of the gnomon of a dial. If the intended 

 prey moved, the spider would keep pace with it as ex- 

 actly as if they were actuated by one spirit, moving • 

 backwards, forwards, or on each side without turning. 

 When the fly took wing, and pitched itself behind the 

 huntress, she turned ix)und with the sw iftness of thought, 

 and always kept her head towards it, though to all ap- 

 pearance as immoveable as one of the nails driven into 

 the w ood on which was her station : till at last, being 

 arrived within due distance, swift -d- lightning she made 

 the fatal leap and secured her prey". I have had an 

 opportunity of observing very similar proceedings in 

 Saltictis scenici/s, Latr. 



But the legs of insects are not the only organs by 

 which they leap. The numerous species of the elastic 

 beetles (FJa/er, L.), skip-jacks as some call them, per- 

 form this motion by means o( vl pectoral process or mu- 

 cro. These animals having very short legs, when laid 

 upon their backs, cannot by their means recover a 

 prone position. To supply this seeming defect in their 

 structure. Providence has furnished them with an in- 



* Evelyn, gutted in lloulvc's Microti-. WO—. 



