In deciding the question as to how often manure should be removed in
cities and towns, it should be borne in mind that when the larvæ have
finished feeding they will often leave the manure and pupate in the
ground below or crawl some distance away to pupate in débris under
boards or stones and the like. Hence the manure should be removed before
the larvæ reach the migratory stage; that is to say, removal is
necessary every three days, and certainly not less frequently than twice
a week during the summer months. A series of orders issued in 1906 by
the health department of the District of Columbia, on the authority of
the Commissioners of the District, covers most of these points, and
these orders, which may well serve as a model to other communities
desiring to undertake similar measures, may be briefly condensed as
follows: