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 (Theridium 13- 
guttatum Rossi), we are told, even attacking the redoubted Scorpion.t 
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, 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 Hiba, p. 31. 
2 “Wen 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 
