"There is a soul of goodness in things evil," I said to a neighbour, an
American lady of English parentage who had come to our verandah; "and the
all-wise Creator has made nothing in vain.  Yet with the fullest faith in
this doctrine, I could never find out of what use the mosquito was, or what
were its purposes in the great scheme of the world."  "Perhaps not," replied
the fair one; "but may not that be your own fault, Mr. Philosopher?  In the
first place, mosquitoes breed in the marshes.  May they not warn us of the
necessity of draining the marshes, and carrying off the stagnant waters, so
as to increase the arable surface of the land?  In the second place,
mosquitoes, in countries where there are no marshes, breed in the running
streams; the larvae of the mosquitoes are the favourite food of young trout.
And if you are fond of trout, why should the trout not have his dinner of
mosquito larvae, to be fatted for your enjoyment?  In the third place, the
sting of the mosquito innoculates, as I have heard say, against the attacks
of fevers that are prevalent in all marshy and undrained countries; and
surely a mosquito-bite is better than a fever, Mr. Philosopher?"

It is always in vain to argue with a lady, so I said no more, inwardly
content that so much could be urged in behalf even of the pestilential
little creature, which was in those days a veritable thorn in the flesh of
me and mine."

Dicken's "All the Year Round."