INDIRECT BENEFITS DERIVED FROM INSECTS. 277 



purpose, except at the timeoflove, is always destruction, 

 in which surely they have no resemblance to the ladies. 

 I have been much amused by observing the proceed- 

 ings of a species not uncommon here, Anax Imperator of 

 Dr. Leach. It keeps wheeling round and round, and 

 backwards and forwards, over a considerable portion of 

 the pool it frequents. If one of the same species comes in 

 its way, a battle ensues ; if other species of Libellidina 

 presume to approach, it drives them away, and it is con- 

 tinually engaged in catching case-worm flies and other 

 insects (for the species of this tribe all catch their prey 

 when on the wing, and their large eyes seem given them 

 to enable them the more readily to do this,) that fly over 

 the water, pulling off their wings with great adroitness 

 and devouring in an instant the contents of the body. 

 From the number of insects of this tribe which are every 

 where to be observed, we may conjecture how useful 

 they must be in preventing too great a multiplication of 

 the other species of the class to which they belong. 



Lastly, under this head, not to dwell upon some other 

 apterous genera, devourers of insects, as the scorpion and 

 centipede, Phalangium and Galeodes, must be enume- 

 rated the whole world of Spiders, extremely numerous 

 both in species and individuals, which subsist entirely 

 upon insects, spreading with infinite art and skill their 

 nets and webs to arrest the flight of the heedless and 

 unwary summer tribes that fill the air, which are hourly 

 caught by thousands in their toils ; one of them ( Theri- 

 dium 13-guttatum Rossi), we are told, even attacking the 

 redoubted Scorpion a . 



So much for the insect benefactors to whom it is given 



a Thiebaut de Berneaud's For/age to Elba, p. 31. 



