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69
Another habit of the fly is its activity. This is so well known as to
become proverbial. Connected with its activity is its range of flight.
This has been ascertained to be about a mile.
The duration of life of the fly is not long. In the winter most flies
die, the remainder hibernate, and at the return of warm weather produce
the first broods of the summer.
Prevention of Disease—The measures which should be adopted to
prevent the spread of disease through the agency of flies are very similar
to those which have been applied with so much success to preventing the
spread of malaria by means of mosquitoes, and consist in (l) destroying
them during the larval and pupal stages of development (2) destroying them
when fully developed, and (3) protecting food against contamination.
It will be remembered that the chief breeding places of flies are
manure and any collection of garbage.
In Deptford there are certain "street refuse" depositories and dungpits
which are uncovered, thus allowing flies to enter freely and
deposit their eggs. If such manure is left undisturbed for nine days,
the eggs will have become fully developed flies ; so that in order to
diminish their number, it will be most effectual to apply preventive
measures during the development stages. In the first place, the dungpit
should be kept covered, so that, if possible, flies may not enter and
deposit their eggs. The larval may be destroyed by adding chloride of
lime to the dung or by spraying the same with a solution of ferrous sulphate,
two pounds to the gallon of water. Both of these will destroy
the larva; and so prevent their developing into adult flies.
In all cases, stable manure should be removed twice a week, and
not deposited within a mile of the Borough, unless the manure is treated
with one of the insecticides above mentioned; and where the object is
not only to prevent development in the Borough, but elsewhere, the
insecticides should be always used when the dung is removed. To sum
up, dung-pits must be so covered as to prevent the fly depositing its eggs
in the pit, and an insecticide added so as to destroy the larvæ as they
are hatched from the eggs.
Flies not only breed in manure as above stated, but also in waste animal
and vegetable substances, commonly known as garbage. Included
in this are house refuse, street refuse and some kinds of trade refuse.
In order to prevent flies breeding in house refuse, it is only
necessary that the bin should be kept covered, and the refuse removed
sufficiently often. It will be remembered that it takes nine days at
least for the eggs to develop into the young fly. A regular weekly
collection of the house refuse will prevent this development.