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tiveness, 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.
Forty-four complaints were received concerning this pest and
thorough investigation and treatment with Dieldrin Concentrate
resulted in the infestaions being considerably reduced. In all 43
treatments were effected involving 236 rooms.
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. Treatment consisted of spraying
38 rooms and 17 exterior surfaces with Dieldrin Concentrate
which produced satisfactory results.
Wasps.—Complaints received implicated three types, the Common,
the German and the Tree Wasp. (Vespula vulgaris, V.
germanica and V. sylvestris.)
Fear of the wasp is often misplaced for they rarely sting unless
they are roused or frightened and, contrary to popular belief,
wasps are not entirely harmful for in spring and early summer
they feed mainly on insects, many of which are themselves injurious.
However, after mid-summer their diet becomes more
vegetarian and the workers feed on ripening fruit and other sweet
substances, thus effecting serious damage in orchards, sugar
warehouses, grain factories, etc., where they cause considerable
wastage of goods. In houses they become a nuisance during
cooking and at meal times and it is conceivable that they are
instrumental in the spread of food poisoning.
The queen wasp, the only survivor from the previous year's
colony, emerges from hibernation in the spring to choose a site
for nesting, usually in cavity walls, lofts, under roof tiles or other
sites which evoke a certain ingenuity on the part of the disinfestors
in order satisfactorily to deal with the nuisance.
Two hundred and twenty-six complaints regarding this pest
were received and during the year some 151 nests were destroyed,
mainly by means of Gammexane powder or Dieldrin Concentrate.