LGR» NORTH AMERICAN INSECTS. 
different species. If we adopt the general rule, that on an 
average three species of Insects dwell on each species of 
plants (and on some plants we find three or four times as 
many), we can easily see that such an enormous number 
can not prove too small an estimate, when we consider that 
there are now known between forty and fifty thousand spe- 
cies of plants. 
The nourishment of Insects is as varied and different as 
that of larger animals. A great number of them are car- 
nivorous, and prey upon other insects; or they feed on dirt, 
dead bodies, or decayed wood, as the dung-beetles, flies, ants, 
and the larve of the stag-beetle; or they feed on plants, as 
the May-beetle, plant-lice, ete. 
“In regard to the venom of Insects, we find a number of 
them provided with organs for biting or stinging, which oc- 
casion inflammatory tumors and poisoned wounds, which 
are ofttimes dangerous, and sometimes fatal to man, as, for 
instance, the sting of bees, wasps, and mosquitoes. 
The faculty called Jnstinct, which belongs to all animals, 
and by which, from an internal impulse, and without in- 
struction, they perform certain actions tending to their own 
support or that of their offspring, is also found in Insects, 
as well as some faculties of the mind which would astonish 
an observer. Thus, when the Tumble-beetle in vain tries 
to roll its little ball up a hill, it runs for assistance, and 
brings back with it two or three other ones who roll up the 
ball in concert with it, but as soon as they have succeeded, 
the assistants fly away, and the first one continues his work 
alone. Bees, Wasps, and Ants defend themselves with great 
courage, and woe to him who attacks a wasp’s nest! Some 
flower-beetles, like opossums, pretend to be dead when you 
catch them, or at your approach conceal themselves behind 
a leaf, or fall to the ground as if dead. Some have even 
memory, and know perfectly well the one who takes care 
of them, as, for instance, the Bees. The nests and dwell- 
