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Description
Order: Coleoptera (‘sheath wings’)

Characteristics:
Forewings hard and leathery, meeting along
mid-line of dorsal surface; hind- wings membranous,
sometimes lacking; biting mouthparts;
well-developed thorax; complete metamorphosis
with egg, larval, pupal and adult stages.

Family: Tenebrionidae
Usually 11-segmented antennae; front and middle
tarsi are 5-segmented and hind tarsi
4-segmented.

Species characteristics:

Lesser Mealworm Beetle (Darkling Beetle)
(Alphitobius diaperinus)
Adults, 5.5 - 6.7 mm long; body, broadly oval,
shiny dark-brown or black; elytra: uniformly
coloured with moderately impressed striae;
underside, dark red-brown; fore tibia strongly
broadened at apex.


Areas where found
A cosmopolitan species thought to have
originated in sub-Saharan Africa. In temperate
areas they are typically found indoors although,
being reasonably cold tolerant, they will survive in
unheated buildings. The Lesser mealworm beetle
is widely distributed in animal houses and
especially poultry houses where the conditions
reflect those of its tropical origin. Infestations are
encountered in deep-pit and deep-litter poultry
houses.

They are associated with a variety of stored
products. Infestations in animal houses may be
introduced by way of contaminated feed. The
insects live in the manure and litter of poultry
houses and are often associated with the feed
and water lines.


Importance as a pest
Lesser mealworm beetles will infest a range of
stored products including cereals, farinaceous
products, oilseeds, groundnuts and bones but are
not regarded as major pests. They are associated
with cereal grains, which have previously been
damaged by e.g. moulds and, where infestations
are encountered in residues, indicate poor
hygiene.

They are of particular significance in animal
houses, especially those where poultry and pigs
are kept. The following problems may be
encountered:
Transmission of diseases and parasites. Lesser
mealworm beetles are vectors and reservoirs for a
variety of poultry diseases including Marek’s
disease and Newcastle disease. They are
intermediate hosts for tapeworms, roundworms
and protozoan parasites and can transmit the
causative agents of bacterial diseases e.g.
Salmonella spp.

Allergic reactions may be triggered following the
exposure of people to the quinones released by
the insects as a defence reaction.
Welfare of poultry. The birds are disturbed by the
presence of the insects. They may feed on the
larvae, which detrimentally affects their food
conversion rate, runs the risk of intestinal
obstruction and puts them at risk of ingesting
harmful organisms. Young, weakly chicks may be
attacked and killed.

Damage to the structure of poultry houses. The
larvae will tunnel earth floors rendering them
uneven and difficult to clean. Significant structural
damage can be caused as the larvae excavate
tunnels in which to pupate. Wall plaster, which is
in poor condition, may be damaged. In particular,
polystyrene, fibreglass and other insulation
materials can be damaged resulting in a
significant increase in heating bills.
Litter may be rendered so powdery that it must
be replaced.

Nuisance may be caused where beetles disperse
to adjacent properties perhaps following the
spreading of manure onto fields. The adults will
fly if the temperature is sufficiently high and are
attracted to artificial light.
The beetles will consume housefly larvae
although they are not generally regarded as a
significant factor in fly control. They will also feed
on the immature forms of Carcinops pumilio so
reducing its effectiveness as a predator on
houseflies. As a result of burrowing, they will
aerate manure, causing it to dry and making it
less attractive for houseflies to breed.


Life-Cycle
Females lay up to 400 eggs in manure, litter,
cracks and crevices in buildings or commodities.
The eggs are about 1mm long and sticky so are
soon covered in debris and cease to be recognisable.
They hatch within a week to give larvae,
which are grey-brown in colour and exhibit a
characteristic “tail horn.” The larvae are very
active, avoid light and feed on litter, manure, spilt
food and even dead or weak birds. There are
approximately 5–11 larval stages and dark banding
becomes more prominent with time. The larvae
are fully-grown after 1–2 months and may be
up to 15 mm long. Mature larvae seek suitable
sites where they can pupate. These include the
fabric of buildings which they may excavate
causing significant damage. The pupae are light
coloured and hatch in about a week, to give
adults which can live beyond a year. Under
optimal conditions the full life-cycle takes about
five weeks.


Control
Assessment of infestations
A variety of trapping techniques are available for
measuring stored product beetle infestations.
These include pit fall traps, bait bags, insect
probe traps and adhesive traps. The population
may be measured by counting larvae on the
fabric of buildings e.g. walls and posts. Samples
of insulation materials can be placed around
buildings and monitored for the entry holes of
larvae seeking pupation sites.

a) Hygiene/management
All sources of infestation should be removed and
disposed of, taking care not to spread the
infestation. Regular removal of manure and litter
from poultry houses will control the beetle.
Routine surveillance and regular cleaning are
important but this can be difficult as the adults
and larvae burrow making them inaccessible.
Care should be taken to ensure that infested food
is not taken into animal houses.
Metal proofing strips provide physical barriers
that can be built into structures to restrict
migrating larvae reaching pupation sites in the
fabric of buildings.
There may be scope for employing insulation
materials which are resilient to the larvae.
Cooling premises to sub-zero temperatures for a
number of days may help to control residual
populations.

b) Insecticidal control
Insecticides (see recommended products) can
be applied to the fabric of infested premises
concentrating on potential insect harbourages
ideally after cleaning. It is difficult to control the
insects in animal houses with insecticides
because they are readily protected by the litter in
poultry houses and as they burrow, whilst
residues can be rendered ineffective by accumulations
of manure and dust. Barrier treatments
can be applied to prevent migrating larvae
reaching pupation sites. Care should be taken not
to kill beneficial insects e.g. Carcinops pumilio.


Advice
Bayer has an extensive range of products specifically formulated for the control of flying and crawling insect pests.

Further information on all Bayer Environmental Science professional pest control products is available from:

Bayer Environmental Science
230 Cambridge Science Park, Milton Road
Cambridge, CB4 0WB.
Tel: 01223 226680 Fax: 01223 226635

The greatest care has been taken to ensure the accuracy of the information contained in this guide. In no circumstance, however, will Bayer Environmental Science be liable in respect of any error or omission.

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