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101
Cockroaches. The cockroach (Blatta orientalis) and its smaller
relative (Blattella germanica) are well known for their destructiveness,
especially in relation to stored organic matter, ranging from
foodstuffs to book bindings. Food is rendered repulsive from
contamination not only with their faeces but also with the
secretion from their scent glands, and the cockroach is strongly
suspected of transmitting to man a number of pathogenic organisms
especially those of an enteric nature.
Cockroaches shun the light and are most active during the
night. Warmth, moisture, darkness and close proximity to food
supplies constitute favourable conditions for breeding.
As was to be expected most of the 83 complaints received con-
cerning this pest came from bakehouses and the three large hospitals
in the Borough; very few originated from occupiers of dwelling
houses. The construction of such premises offers ideal breeding sites
in concealed and almost inaccessible places. Thorough investigation
and treatment with D.D.T. resulted in the infestations being considerably
reduced. In all, 128 treatments were effected involving
623 rooms and 10 external areas.
Clover Mite. Four complaints were received, mainly from
tenants in blocks of flats in various parts of the Borough, concerning
small red or dark brown insects (Bryobia praetiosa) found moving
over walls and windows. A further 9 cases were found on survey
giving a total of 13 during the current year. This was a reduction
of one from the previous year.
The clover or gooseberry mite is harmless to humans and to
household property. It is vegetarian feeding on a wide range of
plants and shrubs and, in some instances, on trees. During the
summer months of July and August the adult females leave their
feeding grounds to seek winter quarters, emerging the following
April to lay eggs on plants in the vicinity. It is during these periods
of migration that they cause concern when they move from their
natural environment into nearby buildings. Some infestations in
fact were reported from houses and flats where natural breeding
conditions were non-existent but where a recent laying of turfs had
occurred in the immediate neighbourhood. On 25 occasions, spraying
of 6 rooms and 24 exterior surfaces with D.D.T. and Kerosene
produced satisfactory results. Such treatment also extended to the
spraying of trees and plants in close proximity to the source of
complaint. A miscible concentrate of malathion has been used
externally on a number of occasions with very good effect.
Wasps. Complaints received implicated three types, the Common,
the German and the Tree wasp. (Vespula vulgaris, V. germanica
and V. sylvestris).