Description
Order: Hymenoptera (‘membrane-winged’)
Characteristics:
Elbowed antennae; biting mouthparts; if
present, two pairs of membranous wings, fore
and hindwings hooked together; abdomen
constricted at base giving appearance of a waist
which bears characteristic nodes or scales;
metamorphosis complete, with egg, larval,
pupal and adult stages; possess complex social
system.
Family: Formicidae
Species characteristics:
Black Ant (Lasius niger)
Workers 3.4-5mm long, queens 15mm long;
colour: workers dark brown-black, queens midbrown;
waist of only one segment.
Distribution
In Britain comparatively few indigenous species,
which nest outdoors, are likely to enter houses
regularly. One such species is the Common black
ant (Lasius niger). An active insect, it nests
outside in grass and walls and under paving. It
will forage widely in search of food, which is
how it comes to enter domestic premises.
Significance
Foraging worker ants cause a nuisance as they
travel widely in search of food, following welldefined
trails and clustering around the food
source. Sweet foods are preferred.
In gardens their excavations around plant roots
make the soil excessively dry. They will also
cultivate greenfly, themselves pests, in order to
obtain the sugary honeydew secretions that
these aphids produce. On the other hand they
can be beneficial as predators of other insects
and general scavengers. They are obviously an
unpleasant sight and may damage food used for
human consumption.
Life-Cycle
The gregarious habits of ants have resulted in
the development of a caste system, whereby
individuals are responsible for specialised duties
within the community. There are: workers
(sterile females); fertile males; and queens
(fertile females). The worker ants build and
extend the nest, look after larval forms and
forage for food, whereby they become pests. The
queens perform none of these duties, but
remain almost exclusively within the nest.
Mating amongst sexual individuals takes place
on the wing. These spectacular swarms involve
large numbers of ants. The actual swarms only
persist for 2-3 hours. After mating the males
perish but the females shed their wings and dig
a cell in the soil where they overwinter.
The eggs are laid in late spring and the white
legless larvae hatch 3-4 weeks later. The larvae
are fed on secretions from the queen’s salivary
glands until fully grown, when they will pupate,
forming the well-known "ant eggs". From these
pupae emerge the first brood of worker ants.
These workers take over foraging duties and
tend subsequent broods. The sexual forms are
not produced until later. The entire cycle takes
about 2 months to complete. Under favourable
conditions a nest may persist for several years.
Control
a) Hygiene/management
Although frequently inaccessible and difficult to
destroy, ants’ nests must be eradicated if
infestations are to be successfully controlled.
The nests of Black ants can be located by
following their trails. Potential food sources
should be identified and protected from attack.
b) Insecticidal control
Insecticide treatments can be applied in and
around the nest and should aim to ensure that
a residual film of insecticide is maintained at
strategic points, for example points of entry to
buildings, such as doors, windows, ventilators,
ducts and drains. Wall/floor junctions, ant runs
and all other harbourages should be treated,
using the preparation according to the label
directions. Particular attention should be given
to small insignificant cracks which may be
major points of entry for the ants. Insecticidal
baits, too, can be used around the entry points.
