Common name: Mealworm, Yellow Mealworm
Scientific name: Tenebrio molitor
(Click on photos to enlarge)
Introduction to bird breeding: Marco
Polo is credited with bringing the mealworm from the Orient to Europe
He used these insects to feed to his birds. Since then they have
spread world wide and are used as a food to a wide range of animals.
- Developmental stages: Egg - Larvae - Pupa - Beetle.
- Sizes: (approx) egg 1 mm, larvae 20-25 mm, pupa 20 mm, beetle
- Colour: Beetles start out
white but soon change to black.
- Weight: about 1000 - 1200 medium "worm" size weigh about 100 grams.
- Adults/Wings = Yes. Flight
= Yes. Flight frequency: Often /
Rarely / Never.
I have not seen a beetle fly in over 25 years.
Fed to: Birds - Most finches, softbills, weavers, whydahs,
waxbills, quail and some parrots. Marsupials, rodents, fish, spiders,
Non breeders: Cost: Between $6 and $10 per 100 grams retail
packs. Upwards of $35 per kilo plus packaging, delivery and/or freight,
if applicable, when purchased from the breeder in bulk. The smaller
the insect size the higher the cost per 100 grams. Available all year
Preferred facilities and husbandry: For
breeders or holding large quantities.
General information: From my view point the raising of
insects is simple if some basic rules are followed. Firstly, put aside
all the ideas you currently have and review what is to come.
Insect production is no different to the production of any other
animals. Give them an environment suitable for their growth and
breeding, plus adequate food and moisture and keep them safe from
predators and minimize disease contamination.
Mealworms prefer a constant even temperature of about 25
degrees Celsius (and that includes 4 AM in the morning in winter when
the owner is snuggled up in bed) with a humidity of about 55% R. H..
An insulated room or cabinet is required to maintain these levels. The
use of 100 mm or 150 mm thick insulated panel walls and roof for larger
breeding rooms is an excellent investment and repays the investment very
quickly with minimal heating costs. The room or cabinet should have a
fan assisted ventilation system to remove the stale air and supply clean
fresh air. Inside the room it is advisable to have a fan operating 24
hours a day to maintain even distribution of heat and humidity. Poor
air movement increases the chances of high humidity pockets and the
likely hood of mould or mildew occurring. Poor air movement increases
the chance of an outbreak of mites. The mites generally do no harm to
the mealworms but mites can be very annoying after handling the boxes,
feeling them crawling up your arms, face and body.
Vacuuming the floor minimizes the build up of mites as they
generally like to spend a lot of their time at a lower temperature than
the mealworms. The vacuum cleaner should be ducted externally to ensure
any pathogens that pass through the vacuum cleaner filters do not get to
contaminate the room. Externally ducted systems remove the possibility
of people inhaling allergens that get through the filters. Inhaled
allergens can , if one is susceptible, cause serious respiratory
problems including triggering an asthma attack. Vacuum the floor at
least weekly and wash the floor with household floor disinfectant.
Clean the walls with a soft cloth about 3 monthly using a mild
disinfectant or a dish washing detergent. The intent of the wall
cleaning is only to remove any build up of dust and fine particles.
Remove and wash the fan grill and blades as required. When vacuuming
look out for spiders and their webs and suck them up.
Without a fan the upper level boxes/trays have a constant higher heat
level than lower boxes therefore influencing faster growth or the
possibility of heat stress on those upper level boxes.
Light: Mealworms do not have a photoperiod regime so it is
not necessary to have timer controls on the lights.
Heating: A good efficient, safe, reliable heater is
essential. Preferably electric as there is no danger of noxious fumes.
Thermostat: A good accurate, reliable, thermostat is also
essential. In larger rooms the installation of double thermostats can
be considered. If a thermostat fails to turn the heater off the
mealworms will start to die at about 38 degrees Celsius. With two
thermostats correctly installed it is highly unlikely both will fail at
the same time.
Externally vented extractor fans: As well as removing stale
air, externally vented extractor fans can be of immense help to rapidly
remove excess humidity especially in summer or excess temperature during
Racks: Painted or surface treated steel racks are good,
galvanized steel racks are even better. Mites do not like the zinc
coating. Timber framed racks are very hard to keep clean and provide
numerous places for mites to hide.
Feed storage: A clean dry place has to be allocated for the
storage of the feeds if they are purchased in bulk. If the feeds are
kept too long there is a strong chance of mites, moths or weevils invading
the feeds. Air tight containers are good for the wholemeal flour and
Rubbish removal: Observe maximum hygiene when disposing of
mealworm wastes. See below: "Respiratory and allergy precautions for
A convenient size for most people to use measures about 600 mm x 400
mm x 125 mm deep. The boxes should be plastic. Plastic boxes are
easily cleaned, light weigh and provided the walls are not scratched or
dirty, the beetles and larval stage will not crawl out. There is no
reason to have lids on the breeding boxes. Lids promote the build up of
mites and high levels of humidity. If one uses the excuse "I need the
lid to keep out the spiders, mice, birds or other insects" then it is
time the environment where the mealworms are kept has to be upgraded to
exclude those pests. The beetles rarely, if ever, fly out of the breeding box if
one has provided a suitable home, diet and moisture for them.
The plastic boxes need only be washed out with dishwashing detergent,
well rinsed and dried with a clean soft cloth. Harsher cleaning
solutions are rarely needed and can damage the surface.
Sometimes the breeding boxes may need the inside walls wiped with a
clean soft moist cloth/sponge/soft disposable paper towel/tissue paper to remove
any build up of food particles or dust like particles. This is usually
required when the humidity drops and small particles may cling to the
interior walls mainly due to electrostatic cling.
Some articles state plastic boxes should not be used due to the
plastic not being able to "breathe" therefore causing a build up of
moisture causing moulds to develop. They also advocate the use of tight
fitting lids with a few mesh covered holes so beetles or the larval stage
cannot crawl out.. I disagree strongly with these assumptions and
that the beetles will rarely fly (in 25 years of breeding mealworms I
have never seen a beetle fly) if their home is to their liking.
Beetles and larva cannot climb up smooth clean surfaces. So why the
need for a lid?
Timber is heavy and hard to clean. That may be so, but, if timber,
chipboard/mdf, masonite and plywood is
painted or coated with a waterproof material it is then not able to
"breathe", giving it the same characteristics as plastic.
Painted timber, chipboard/mdf, masonite and plywood, is easy to clean
with a moist cloth/sponge. A bit of good quality dishwashing
detergent added to the water can help. Take care with a timber box
and it will last a lifetime.
Drop a plastic box and it can break or crack. Plastic boxes over
time can become brittle.
Do not use chlorine based cleaners on plastic as it can remove the
smooth/shiny surface and the beetles may be able to crawl out. The
longer and the more concentrated you use the chlorine cleaner the
rougher the surface may become.
over time, may eat holes in unpainted timber or chipboard/mdf but these
small holes can be filled with a non-toxic timber filler.
In cricket breeding boxes, the hatchling
crickets can easily walk up a box that has been only cleaned a few times
with strong chlorine bases products. Their feet are very small and
have no trouble with what looks to us like a smooth surface.
It is the operator, not the box material
that makes the system productive!! Timber, chipboard/mdf or
plastic, it does not matter!!
Mouse proof wire mesh (approx 6.5 mm) can make a suitable cover to
place over a box that is in a place vulnerable to attack from mice,
rats, birds etc. Any beetles that try to fly out will usually just hit
the wire and fall back to the hessian surface. Mouse proof wire allows
near perfect air movement over the surface of the colony. Mites love to
breed in boxes with poor air movement (i.e. high humidity).
The ideal diet for
the continual production of mealworms in a room at about 25 degrees C
and about 55%R.H. comprises bran, wholemeal flour and dry inactivated
yeast. The proportions are by weight 80 % bran, 15% wholemeal flour
and 5% yeast. These ingredients are thoroughly mixed and placed into
the clean box. About 70 - 90 mm deep layer in a box with a wall height of
about 125 mm is all that is needed. Always keep the level of the feed about
mm below the top of the box. After the dry feed has been placed into
the box, use a clean moist cloth or moist soft disposable paper towel to
remove any feed that has clung to the internal walls. More food can be
added as the level drops or the feed is all consumed but ensure level
does not get within 40 mm of the top. For optimal growth rates, top up the box with the same mix
as initially supplied if they consume all the food in that box.
Caution: The dry powdered inactivated yeast is a very fine
powder that can easily become airborne if handled roughly. If the
fine yeast powder is inhaled it may cause respiratory problems in some
people. For me it causes asthma like breathing restrictions.
Treat it carefully and it is not a problem product. Wipe surfaces
with a damp cloth/sponge that are dusted with the mealworm food mix.
Place one or two layers of hessian on top of the feed. Leave
about 10 mm between the edge of the hessian and side walls. It is
not necessary to place any paper, hessian or similar material at
levels other than on the top of the feed.
The provision of
moisture is probably the most important aspect of insect production.
Some articles recommend the use of raw carrot or raw potato. I do not
recommend the use of any vegetables that grow underground. If one is
breeding mealworms on a continual basis I feel it is a possible vector
for bacterial and/or pathogen infection. For short term use with non-breeding colonies
it should be O.K. Most other fruits and vegetables that are grown
above ground level are O.K. Remove
uneaten vegetable or fruit material after 24 hours or at worst after 48
hours. Mealworms are a pest in grain storages. They will eat
damaged grain. They do not normally live on the ground or in the
ground and do not have the tolerances for soil borne diseases and
If small numbers of boxes are involved then the use of water
moistened bread is ideal. Sliced apple works well. As you learn more
about the system, it is possible to use water and spray it directly onto
the hessian. The mealworms will come up and drink the water. Problems
occur if too much water is used, mould will grow in the bran mix. Too
little and the mealworms will go thirsty.
Hessian. One or two layers
of hessian can be placed on top of the bran mix to prevent the moisture
source from disappearing into the bran mix. If there is no
material to prevent the moisture source from disappearing into the bran
mix, and, if all the fruit or vegetable matter is not eaten, the
residual moist matter can mix into the bran, decompose and be a source
of contamination for the colony.
Mealworms can chew, suck, or shred the hessian to obtain the moisture
that soaks into the hessian and the end result is a layer of fluff like
material. (Click on photo to enlarge)
If the beetles get adequate moisture they rarely, if ever, fly out of their
Photo shows colour phases from white new beetle
to dark final colour. (Click on photo to enlarge)
Beetles live for
between one and three months. Females lay a lot of eggs and under good
conditions about 100 hatch and develop to adulthood. Beetles do require
a constant supply of moisture and love eating moistened bread.
Place about 250-300 beetles in a box 600 mm x 400 mm
(24 x 16 inch). This should
produce about 1200 grams of medium size larval stage. The beetles must
be placed in a freshly prepared box as outlined above. Do not leave
them in their original box as they will only eat the pupae or eggs.
Surplus beetles can be fed to birds and other animals.
In over 25 years of breeding mealworms, I have never seen a mealworm
beetle fly. I have observed them raise their wing covers but never
get airborne. The only way they leave a box is by walking/crawling
up the wall. The box wall has to be very smooth and clean.
If the wall is scratched, dirty, has a spider web on the surface, or the
hessian is too close to the top, the beetle may get a good foot hold and
After they have got to the top of the box and fallen off, they just fall
to the floor without flying.
Photo shows large larvae just prior to pupating and
several pupa. (Click on photo to enlarge)
Pupa can be removed from
the original box and placed under the top layer of hessian in a fresh
box or left in the original box till they develop into beetles. Excess pupa can be fed to
birds and other animals. Pupae develop to beetles in about 10-14 days
depending on temperature. If mites build up they can easily overcome a
pupa and eat the pupa (a mite build up is a hygiene and or humidity
problem). Mites also feel horrible when they start to crawl up
your feet or hands. Mites also leave an unpleasant smell on your
hands or clothing.
If the mealworm box has two layers of hessian on the top of the bran
mix, the mealworms like to turn into the pupa stage while they are
between the two hessian layers.
If only one layer of hessian is used, the pupa will be found on the bran
surface just below the hessian and often at the outer edges of the
Photo shows large mealworm larvae plus some shed skins.
(Click on photo to enlarge)
The "worm" stage can last from 50 days to over 12 months depending on temperature, food
and moisture availability. If inadequate moisture levels are not
maintained the larval stage will eat the papa stage or any eggs they may
find. The beetle and larval stage can be cannibalistic. If
overcrowding is evident, remove some and either feed them out or put
them in a new box. If in a box, the eggs fail to hatch or the worms
fails to thrive it is generally best to dispose of the entire contents
of the box, thoroughly clean the box and start afresh.
"Mini Mealworms". In Australia, "mini" mealworms are just
small mealworms. Sieve the frass from a batch of mealworms then
place the mixed sizes onto a 10 mesh wire sieve. The ones that
fall through are classified as "mini's" and the ones that do not fall
through are mostly "regular" size. The larger ones can be fed out
and the "mini's" can be replaced into a fresh box to grow or can be fed
to the birds that prefer small mealworms.
If you purchase a retail container of "mini" mealworms, remove them from
the container and place them into a larger well ventilated container.
Add more bran if required. Mini mealworms can become dehydrated
very quickly and easily. To give them a quick easy feed of
moisture, just place a slice of water moistened (moistened, not wet)
bread on top of the bran. Remove any damp uneaten bread after 24
Lesser mealworms (Alphitobius) are a different species and do not
grow much bigger than 12mm ( half inch) long. Do not mix Lesser
mealworms and the normal mealworms as the lesser mealworms will soon out
compete the normal variety. They can be treated the same as the
usual mealworms. Lesser mealworms beetles are much smaller than
Tenebrio molitor and they like to fly. You will find the beetles
everywhere after a few hot days.
Mini mealworms and regular size mealworms can rapidly dehydrate if they
are placed in a refrigerator. They need to be removed from the
fridge every few days and allowed to have 12 or so hours of room
temperature plus a feed to maintain good health. If mealworms
dehydrate, their shape will change from a plump round waist line to a D
shape. By that I mean their underside becomes flattened and they
often appear a darker colour. There is little or no "juice" in a
dehydrated mealworm, so there is minimal value in feeding dehydrated
insects to most birds or animals.
Most mealworms will quickly re-hydrate if they are given a suitable food
and moisture source at room temperature of no more than 25 degrees.
They can quickly regain the round shape. Give them a day or two
and they will be ready to be fed to your birds or animals.
The food or bran in a refrigerated container can become wet from
condensation from within the container. If condensation or wet
bran is observed in a container, do not replace that container back into
the fridge. Either replace the mealworms into fresh bran or allow
the bran in the container to dry before replacing it into the fridge.
If insects are placed into a
household freezer, the fats in the insect bodies will start to break
down. The fats are converted into a "soap like" compound.
The fats will even break down in commercial freezers that cool to below
minus 20 degrees C. Household freezers are often only about minus
4 degrees C. This tissue breakdown is undesirable and it can also
change the taste, smell and flavour of the insect. Some birds or
animals will not consume an insect that has been frozen for more than a
few days. Refrigerate in favour of freezing. Feed live
insects in preference to dead insects.
The eggs when laid have a
sticky coating and are either deposited onto a solid surface (including
the hessian) or get coated in the dry feed or frass. When coated they
are about the size of a "hundreds and thousands" cake decoration. Time
to hatch is about 10 to 14 days depending on temperature.
food and moisture is available, the higher the temperature (up to about
35 degrees) the faster they grow. An ideal temperature is about 25
degrees. This will allow a good growth rate with minimal problems. At
about 25 degrees the cycle should take no more than 10 - 12 weeks.
To harvest small
quantities just place a slice of fresh bread or several crumpled layers
of moistened paper towel on the surface. Within a few minutes they will
commence eating the bread or crawling in the damp paper towel. Pick up
the material and shake off the mealworms and repeat the procedure till
the required quantity is obtained.
To obtain larger quantities it is better to put the entire contents
of the box through a fine sieve. To obtain the size you require, select
an appropriate sieve screen size and gently re-sieve. Place the unused
portion in a clean box with a small quantity of fresh feed mix and
return them to the breeding room. Carefully dispose of the sieved waste
Escapees will not flourish outside a heated breeding room and all
outside escapees usually die over winter. Do not bring the bird insect
tray to the insect room as the same type of mites that colonize the
aviary floor can also infect insect breeding boxes and breeding rooms.
Bring the insects in a container to the birds and give the container a
wash before returning it into the insect production area.
For birds, most
insects are usually offered in a smooth shallow tray. If woodroaches
are to be fed to birds an additional step has to be taken. Add a non
sticky escape proof barrier (Fluon) of about 50 mm wide all around the
top of the inside wall of the tray as per breeding boxes (otherwise they
will all run away). A layer of sand or bran can be placed into the tray
to give the birds a more secure footing when they land in the tray.
Some people place the insects in a deeper smooth sided tray (e.g.
600mm x 400mm x100mm deep) which has been partially filled (20 or 30 mm
deep) with clean leaf litter, dry leaves or a material such as dry peat
moss. Most insects dislike light so they will move to the bottom of
the tray. This allows the birds to "hunt" for the insects and can
provide them with entertainment, activity and exercise as well as
preserving some of their natural instincts.
If a plastic or metal tray is used such as the 600mm x 400mm,
place it on some strips of timber or other material to raise it off
the ground and allow air to circulate under the tray. Escapees will not
flourish outside a heated breeding room and all outside escapees usually
die over winter. Do not bring the aviary insect tray to the insect room
as the same type of mites that colonize the aviary floor can also infect
insect breeding boxes and breeding rooms. Bring the insects to the
birds and animals in a container and give the container a wash before
returning it into the insect production area. Fluon (250 ml.) is available from The Herp Shop (Melbourne, Vic.)
(03) 9363 6841
Storage of small quantities:
I do not advocate the refrigeration of mealworms. Purchase a smaller
size, keep them in a cool place and they will grow at a much reduced
If you need to place mealworms in to a refrigerator to slow the growth
rate, or during very hot days, refer to the comments as listed in the
topics "Refrigerating mealworms" and "Freezing insects" which are a few
topics above this paragraph.
Dehydration can kill refrigerated mealworms.
The food in a refrigerated container can become wet from condensation
from within the container.
Disease and infections:
Rule - If any mealworms fall onto the floor they must NEVER be placed
back into ANY boxes!! Throw them out or feed them out!! The disease
contamination risk is far too high!!
Mealworm colonies can be wiped out by a variety of diseases caused by
viruses and bacteria. Moulds, fungi, internal and external parasites
can quickly wipe out a colony. Mites are generally an indication of
either poor hygiene or poorly controlled environmental factors. Mites
can be a vector for the spread of diseases. Government animal pathology
laboratories and some private pathology laboratories are able to
identify insect diseases and recommend appropriate treatments. Over
crowding is one of the most common triggers for the outbreak of diseases
along with contaminated feed. Dirty contaminated hands and equipment
will rapidly spread an infection throughout the room.
Golden rule : If you have a colony of insects that are
breeding well, do not add any stages of the mealworms from any other
outside source and in no circumstances allow any of the foreign frass or
feed material into any of the places used for breeding your mealworms.
Some commercial breeders and research laboratories have continuously
bred mealworms for over 20 years without the need to introduce new
If it becomes absolutely necessary to introduce more insects to your
colony, make sure appropriate quarantine procedures are implemented.
Place them in a box of their own and not into a current colony. If
anything bad happens in that box , dispose of all of the quarantined lot
and implement strict disinfection procedures. A bacterial infection can
easily kill 96% or more of a colony and eradication can be a long
arduous task. At 25 degrees, parasites, pathogens and mites can
multiply at an amazing rate.
My philosophy is: prevention of disease outbreaks is better than
having to cure the outbreaks (It's also cheaper).
Respiratory and allergy precautions for humans:
The following is applicable to all insects.
As stated above, the dusts in the breeding room and any fine insect
tissues, when inhaled, can cause reactions requiring medical
intervention. The longer one inhales the contaminant the more severe
the reaction can be. The effect can be cumulative and the longer you
breath it in, the longer it may take to cure (sometimes years). The
main contaminant is the (4) proteins in the insects frass (droppings/
excrement). When this material is inhaled into susceptible peoples
lungs, they may react badly. General rule is never keep a breeding
insect colony in a residential house.
It is unwise to use a broom or similar cleaning product in the
breeding room to clean the floor as it is likely to stir up dust which
can be inhaled or settle in a breeding box or on other equipment
resulting in a disease outbreak.
When it comes to disposing of the frass (excrement) from mealworm
boxes, cricket boxes, woodroach/cockroach boxes or the locust
cage, take every conceivable measure to minimize the inhalation of any
dust or material and to prevent its spread to others. A wise precaution
is to shower and wash your hair if you get contaminated. Pop the cloths
into the washing machine for a good wash before using them again. Never
go to bed with "bug dust" in your hair as you will inhale it throughout
the night from on your pillow.
Locusts cause more health problems than most insects, both skin
rashes and inhaled respiratory ailments.
While handling mealworms, do not rub your eyes as the fine material can
have an adverse reaction and cause strong eye irritation. Wash hands
and any exposed areas to minimize the risk of skin irritation after you
finish your tasks.
Most people tolerate some
degree of contamination but if you exceed the "trigger point threshold"
and get a bad reaction, seek medical attention and tell the
medico what you have been inhaling. Medical respiratory allergy
specialists are available in Capital cities if required.
My philosophy is: prevention of possible health problems is better
than having to cure a real health problem (It's also cheaper).
Now that you have read this far I will answer 2 of the most commonly asked
Where do the mites come from?
Mites are everywhere people breed
birds. It is impossible to get rid of all the mites. The
floor of an aviary has millions of these little nuisances as part of the
normal floor ecology. When one walks into an aviary, the mites
will climb aboard our feet, clothing or hands and get a free ride into the insect
Mites coming in on the foods we feed to the mealworms is the least
significant vector for contamination. You don't have to heat or freeze the
mealworm foods to "get rid of the mites". Its a waste of
time and energy. If there was any mites
on those foods the mite numbers would be insignificant compared to the
mite numbers in a normal aviary. Always purchase insect
foods from a reliable supplier and do not too big a quantity during the
cooler, damper months. Always store the insect foods in a dry
place and not in the room with the insects or the aviary.
How do you get rid of mites in the boxes?
The removal of mites is quick and easy!!
It is impossible to totally remove all mites from a mealworm breeding
room. It is impossible to prevent more mites entering a bug room.
A mite build up is usually a hygiene and or humidity problem.
If mites build up they can easily overcome a pupa and eat the pupa. They also feel
horrible when they start to crawl up your feet or hands. They also
leave an unpleasant smell on your hands or clothing. That was
The easiest way of reducing a mite problem is to vacuum the floor on a
daily basis and to remove about 50% of the frass from the box.
The established boxes that are mostly frass (bug poop) are the boxes
that usually cause the mite problem, or are the origin of the problem.
Removing most of the frass from each heavily infected box by carefully sieving, almost
always removes the problem. After sieving out the frass, dispose
of the frass carefully.
Replace the box back into the bug room and add some more food.
The next action is to temporarily reduce the humidity to no more than about 50% R. H.
and put the temperature to about 25C. The reduced humidity and
correct temperature usually encourages the other mites to "disappear".
Don't know where they go, but with regular vacuuming the problem quickly
disappears. Ideal humidity level for an insect room is about 55%
A/A Vol 59 No. 8 Aug 2005 Page
- A/A Vol 55 No. 2 Feb 2001 Page 32-35
- A/A Vol 48 No. 1 Jan 1994 Page 22
- A/A Vol 32 No. 2 Feb 1978 Page 17
- A/A Vol 28 No. 1 Jan 1974 Page 13-14
- A/A Vol 18 No. 8 Aug 1964 Page 120 (USA).
- A/A Vol 15 No. 1 Jan 1961 Page 16.
- A/A Vol 14 No 4 Apr 1960 Page 61-62.
- A/A Vol 13 No 5 May 1959 Page 69-70.
- A/A Vol 10 No 3 Mar 1956 Page 29-30.
- A/A Vol 8 No 10 Oct 1954 Page 114-119.
- A/A Vol 8 No 9 Sept 1954 Page 110.
- A/A Vol 7 No 7 Jul 1953 Page 88.
- A/A Vol 5 No 9 Sept 1951 Page 104-105.
- A/A Vol 4 No 1 Jan 1950 Page 12.
- A/A Vol 3 No 1 Jan 1949 Page 7-8 (a good article!).
- A/A Vol 1 No 8 Aug 1947.
- Australian Birdkeeper
- ABK Vol 1 Issue 6. Dec-Jan 1989 Page 182
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