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COMMON LODGING HOUSES.—The two common lodging houses in the Borough ceased to
operate in 1942, and 37 visits of inspection were made during 1939-42.

MOSQUITOES.—In 1939, complaints were received from residents of whitton and the
Twickenham Road area of Isleworth of the presence of biting mosquitoes. Specimens caught were
identified as culex pipiens. As this mosquito does not bite man further specimens were sent to the
British Mosquito Control Institute, where the mosquito, culex molestus, was identified.
This mosquito, which closely resembles culex pipiens, was first described in Paris in 1930. It
was identified in this country at Hayling Island in 1934, at Westminster in 1935, at Battersea,
Bermondsey, Chelsea, Deptford and Greenwich in 1938, at Isleworth in 1939, and in stagnant water
in the London Underground Railways in 1940. In 1943 it was found in West Ham, Richmond and
Twickenham. A carefully detailed examination by an expert is necessary to distinguish the adult forms
of culex molestus and culex pipiens. The larvae are identical in appearance, and the usual method
of identifying is to watch the behaviour of the adult mosquitoes reared from the larvae. Adults
developed from molestus larvae will mate and lay eggs without having had a meal of blood, whereas
in the absence of a blood meal adults from pipiens larvae remain sterile. Thus it may take a week or
so to ascertain if culex molestus is breeding in any larva-infested water. Experience in the underground
railways confirmed the previous indications that the favourite breeding place of culex molestus
is in dark and warm underground situations.
Since 1939, larvae from the following sources in the Borough have been identified as culex
molestus: warm dark recesses under boilers, underground passages in a sewage works, and ponds,
tanks, water butts, etc., in gardens and allotments. Constant attention has been given to Mogden
Sewage Works, but on one occasion only (1943) has culex molestus been found breeding there.
Sanitary Inspectors have spent much time searching for possible breeding places, and larvae from many
sources have been collected and the behaviour of the adult mosquitoes hatched therefrom observed
with a view to confirming or otherwise the presence of culex molestus. To date, this mosquito has been
found most frequently in allotment tanks, but as these are probably second breeding places the search
for the main breeding place continues. This fierce persistent and vicious human biting mosquito is a
serious nuisance, and as it has been less prevalent in 1945 and 1946 than in previous years, it is hoped
that some progress is being made towards its eradication. The co-operation of all industrial concerns,
gravel pit owners, gardeners, allotment holders, etc., by treating all stagnant water with paraffin,
D.D.T. or other larvicide would do much to discourage mosquito breeding.