32 NATURAL HISTORY OF WASPS. 
biographer of the late Sir Thomas Brisbane, has 
assured me that the practical result of destroying all 
the wasps on Sir T. Brisbane’s estate was, that in 
two years’ time the place was infested, like Egypt, 
with a plague of flies. At every wasp’s nest you 
might have gathered a handful of the wings of 
insects ;* and the flies throve apace when the wasps 
were killed. 
We do not readily appreciate the indirect benefits 
which we derive from the labours of wasps, just as 
we are not perhaps properly grateful to beasts of 
prey for their equally unsolicited assistance. Cats, 
and weasels, and foxes, though they are not good 
to eat, are often much more acceptable neighbours 
to the farmer than rabbits. And the colonist, brought 
into contact with nature in her wilder forms, knows 
well how the larger beasts of prey serve hm by 
keeping m check the animals of which he more 
immediately and consciously makes use, but which 
very animals, without these restrictions, might prove 
more injurious to him than beasts of prey ever do. 
As Man takes possession of the soil, the beasts of 
prey retire before him, and we, in a certain sense, un- 
dertake their duties. The duties of insects, however, 
are not so obvious, nor so easily within our power 
to fulfil. We scarcely know what we owe to them 
so long as they confine themselves to the fertilization 
of flowers, to destroying decaying organic matter, 
or to keeping each other’s numbers within due bounds. 
It is when they exceed these limits, when they hurt 
* T acknowledge with great pleasure Mr. Bryson’s kind communiea- 
tion in further explanation of his letter in ‘The Times,’ On behalf of 
wood-pigeons and sparrows, December 17, or later, 1864. 
