INDIRECT BENEFITS DERIVED FROM INSECTS. 159 



suddenly darts forth the mask, opens the forceps, seizes the unfortunate 

 victim, and brings it within the action of its jaws. 



When they assume the imago state, their habits do not, like those of 

 the white ants, become more mild and gentle, but, on the contrary, are 

 more sanguinary and rapacious than ever ; so that the name given to them 

 in England, " Dragon-flies," seems much more applicable than " Demoi- 

 selles," by which the French distinguish them. Their motions, it is true, 

 are light and airy ; their dress is silky, brilliant, and variegated, and trimmed 

 with the finest lace : so far the resemblance holds ; but their purpose, 

 except at the time of love, is always destruction, in which surely they 

 have no resemblance to the ladies. I have been much amused by ob- 

 serving the proceedings 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 

 Libellulina presume to approach, it drives them away, and it is continually 

 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 everywhere 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, Galeodes, 

 must be enumerated 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 (Thendmm 13- 

 guttatum Rossi), we are told, even attacking the redoubted Scorpion. 1 



So much for the insect benefactors to whom it is given in charge to 

 keep the animals of their own class within their proper limits ; and I 

 cannot doubt that you will recognise the goodness of the Great Parent in 

 providing such an army of counterchecks to the natural tendency of almost 

 all insects to incalculable increase. But before I quit this subject I must 

 call your attention to what may be denominated cannibal insects, since, in 

 spite of those declaimers who would persuade us that man is the only 

 animal that preys upon his own species 8 , a large number of insects are 

 guilty of the same offence. Reaumur tells us, that having put into a glass 

 vessel twenty caterpillars of the same species, which he was careful to 

 supply with their appropriate food, they nevertheless devoured each other 



1 Thiebaut de Berneaud's Voyage to Elba, p. 31. 



2 E'en Tiger fell and sullen Bear 



Their likeness and their lineage spare. 

 Man only mars kind Nature's plan, 

 And turns the fierce pursuit on Man." 



Scott's Rokeby, canto iii. 1 



