Mealworm Beetles are considered scavengers and are among the largest insects
that infest stored products. Most prefer to feed on decaying grain or
milled cereals in damp, poor conditions. These insects are usually found
in places not frequently disturbed such as dark corners, under sacks,
in bins and where feed is stored. Indoors, they are usually found in basements
or at grade level, sometimes infesting cornmeal, flour, cake mixes, cereals,
meat scraps, dead insects, bran and litter from chicken houses, they have
even been found in sparrow's nests where they feed on the droppings. Mealworms
have been found living under old carpeting and in straw-stuffed chairs
in damp areas. Yellow mealworm larvae are known as "golden grubs" (see
above) and make excellent fish bait and serve as food for animals in aquariums
and zoological parks.
larvae are white, darkening with age. Larvae of yellow mealworms are honey-yellow,
while dark mealworms are dark-brown.
have a smooth, highly polished, shiny, elongate, hard, cylindrical (wormlike)
body about 1/8 inch thick and up to 1.25 inches long at maturity. Beetles
are robust, black and nearly 3/4 inch long, resembling many ground beetles
in size, shape and color.
mealworm adults are shiny, dark-brown or black, whereas dark mealworm
adults are dull, pitchy black. Eggs are white, bean-shaped and about 1/20
inch long. Pupae are white at first, turning yellow, and are not enclosed
in a case or cocoon.
adults do not move as fast as ground beetles. Also, the hind leg of a
mealworm adult has only four tarsal segments, while the hind leg of a
ground beetle has five tarsal segments.
is another species of mealworm known as the Dark Mealworm (Tenebrio
obscurus). Young larvae are white, darkening with age. Larvae
of yellow mealworms are honey-yellow, while dark mealworms are dark-brown.
The difference between the adults is shown in the pictures below with
the Dark Mealworm Beetle being on the left:
courtesy of Ohio State University
Cycle and Habits:
beetles are black or dark brown and they feed as larvae and adults on
grain products. T. molitor is an important post-harvest
pest and occurs spread all over the world. Adult beetles are attracted
to night-lights, are strong fliers, and are found in dark places. Each
female lays about 275-600 eggs, which hatch into larvae in 4 to 14 days.
Eggs are laid singly or in clusters during the spring over a period of
22 to 137 days. Larvae firstly eat the germs
of stored grains and can feed on a wide variety of plant products such
as ground grains, flour, tobacco and foodstuffs. Larvae are very voracious
and highly resistant to low temperature; they can remain alive for 80
days at -5°C. Larvae
may spend up to two years in this stage depending on the environment.
Individual larvae may wander far from the food source to pupate, making
it difficult for homeowners to locate the source of infestation.
larvae mature by fall, overwinter and pupate in the spring, with the pupal
stage lasting 7 to 24 days. Adults emerge in the spring and early summer,
living two to three months.
warm summer evenings they often fly in through the open windows attracted,
as we've already said by the light. They normally do no harm in the living
rooms of houses and as they take so long to develop they do not become
a problem in domestic kitchens.
are not always considered pests since some people raise them for fish
and animal food.
good night-light discipline to reduce beetle attraction and infestation
indoors (in the countries where this applies). Sanitation is the simplest
means of controlling mealworms. Moist, dark, undisturbed areas containing
damp grain or milled cereals should be eliminated. Litter remaining in
old or abandoned poultry houses can create explosive infestations, bothering
residents as far as 1/2 mile away. Poultry litter dumped into piles outdoors
can result in mealworm migrations indoors. Waste grain products in a sanitary
landfill may become a source of infestation.
the measures taken to prevent this pest in an industrial environment
should be on-going anyway and if allowed to get to the point where they
are a major problem, then fumigation would be the only alternative.
But as I've said before.....Housekeeping, Housekeeping....etc.
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