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curves for "All flies and Musca" are plotted out to a scale which differs from that employed for "Other
species." Study of this Diagram and of Diagram III. shows that Homalomyia canicularis has a
seasonal curve which deviates notably from that of Musca domestica; indeed, while some 20 per cent.
or more of the flies caught in June were specimens of Homalomyia canicularis, less than 1 per cent.
of those caught in October belonged to that species. It will be seen on study of Diagram III. that
a much larger percentage of Homalomyia was obtained in the case of certain centres, notably in that
of centre 8, the glue and size factory. At this centre, moreover, specimens of an unusual species of
fly were not infrequently encountered (see page 2 and Diagram III). At two of the centres considerable
numbers of Stomoxys calcitrans were secured. At one of these centres (centre 7), a cowshed,
vast numbers of this fly were found in the shed throughout the summer. At a cowshed near to the
other centre in question (centre 6), a considerable, though much smaller, number of Stomoxys was
caught. In the neighbourhood of two other centres, two single specimens of Stomoxys were encountered.
In the cases of the two cowshed centres, Stomoxys calcitrans was found only in the sheds ; no
single specimen was obtained in a living room in the near neighbourhood of the sheds. It will be
necessary to recur to this point later. No Stomoxys calcitrans was found in places of observation
surrounding five of the nine centres.
2.—As to comparison, made last year, between centres where the influence oj horse manure was
very pronounced and the remaining centres.
In 1907 there were four "stable centres" and eight "other centres." In 1908 there are four
"stable centres" and five "other centres." In 1907 the curve for "stable centres" did not reach
its maximum until the end of September, that for the other centres had already attained a maximum
rather more than one month earlier. In 1908 the behaviour of the two curves up to the middle of
August will be found to be similar to that in 1907 (provided, in making the comparison, the differing
proportions of "stable centres" to "other centres" in the two years be allowed for). While in the
later year, however, both curves show decline after that date, with a slight rise at the end of September,
in the earlier year the "stable centres" do not show this decline, but the curve steadily ascends to its
maximum at the end of September. There is correspondence in the two years in one respect, the curve
showing average yield of flies per "stable centre" runs at a higher level, from mid August to the end of
September, than does that showing the average number for the "other centres." In 1907, the "superadded
wave" manifested in the curve giving totals for all centres, was thus due in the main to the maintained
rise of the curve for the stable centres," and it was suggested, inasmuch as the influence of
stable manure had undoubtedly made itself felt at the "other centres" (though to less extent than
at the "stable centres"), that, if the said influence could be entirely eliminated from the other
centres, the "superadded wave" of late September would disappear from the "other centres"
curve. In other words, there were two distinct seasonal curves—one for "other centres" having its
maximum towards the end of August, and one for "stable centres" having its maximum rather
more than one month later, just at the end of September. The latter wave was further attributed to
the " breeding of batches of flies in horse manure, during the close of the summer and early
autumn."
The observations of 1908 raise the question as to the influence in this connection of the
differing seasonal distributions of Homalomyia and Musca. Thus Homalomyia attained a maximum
on August 7th (see Inset in Diagram I.), and then fell off, so that by the end of the month of August
only a very small percentage of the flies caught belonged to this species. The maximum for Musca
was not attained until August 14th, and further the decline of Musca was less marked during the latter
part of August than that of Homalomyia. Thus it might be suggested that the differing seasonal
curves of Musca and Homalomyia account for the slightly marked superadded wave of 1908
and the more marked superadded wave of 1907, and therefore account in some degree for
the differing behaviour of the "stable centres" and "other centres" curves. The differing
seasonal curves of the two species do not, however, wholly explain the want of correspondence in the
"stable centres" and "other centres" curves. The numbers of Homalomyia are throughout much
smaller than those of Musca, and, as a matter of fact, if Homalomyia be excluded from consideration
altogether, and the numbers of Musca alone taken, the differences in the "stable centres" and "other
centres" curves are still exhibited. Thus the "breeding of batches of flies" (and we may now go further
and say of Musca domestica)" in horse manure during the close of the summer and early aututmn" is
no doubt in the main responsible for the differing behaviour of the curves for "stable centres" and
"other centres" respectively. The part played by stables in determining fly prevalence is indeed one
of paramount importance; and inasmuch as some stables are much more productive of nuisance than
others, question arises as to whether efforts should not be made to secure uniformity both as regards
compliance with a proper standard in respect to sanitary conditions and further as regards regular
removal of manure.
3.—As to the mutual antipathy of the various species oj house fly one to another.
It was noted quite early in 1908, by one of the Council's inspectors, Mr. Tuck, that specimens
of Homalomyia were, as a rule, present on a particular part of the paper, viz., at the lower margin. This
inspector's practice had been to fold back a strip about ¾ inch in breadth at the lower part of the paper
and then to turn over the two corners (see Diagram IV). This expedient was adopted with a view to
providing a means for catching "honey gum" which trickled down from the surface of the paper to its
lower part, as otherwise the sticky gum was apt to fall upon floors, tables, etc., and cause annoyance.
The lower ¾ inch of fly paper exposed would under these circumstances be the back, not the front of
the paper, and the surface would therefore not be a gummed one. Mr. Tuck, however, had further adopted
a practice of again folding back this strip, so as to bring its ungummed surface into contact with the gum