Raising mealworms for animal food
by Dr. Adrian Lawler
(retired) Aquarium Supervisor (l984-l998) J.L. Scott Aquarium Biloxi, MS 39530
Aquarticles
Yellow mealworm (Tenebrio molitor L.) larvae are sometimes called "golden
grubs" and make good fish bait; larvae and adults serve as food for animals (birds,
frogs, turtles, lizards, fish, etc) in aquariums and zoological parks, and are relatively
easy to raise. They can supplement the diet of various animals, or be a major part of the
food of some toads, frogs, lizards, etc. held in captivity.
Length of the life cycle is 3-5 months, depending on various factors as food,
temperature, moisture, etc. The larval stage may include 9-20 molts. The beetles and
larvae eat decaying leaves and plant matter (occasionally new plant growth), dead insects,
feces, cornmeal, flour, cake mixes, cereals, meat scraps, bran, stored grains, etc., and
litter found in chicken houses, bird nests, and animal nests.
Here I present a brief summary of one way to raise mealworms:
1….Construct two rearing boxes with the following characteristics (I prefer wooden
boxes, but ventilated plastic boxes could be used):
A….4-6 inches deep…..length and width can be varied to suit
your rearing space, and the size of your production operation. I used boxes that were
about 6" by 14" by 24" and they provided enough larvae and adults to feed
many animals in a public aquarium 1-3 times per week.
You need either 2 boxes or 2 sections in one box in order to have a place to put the food
and debris (with included eggs and larvae) from one box when you clean it so that eggs and
larvae are not lost and your production set back.
B….Attach legs of length you want to corners of box (about
24").
C….Place each leg into a small container containing water as a
deterrent to keep ants from climbing up legs and getting into your culture.
D….Attach a screened (for ventilation, and to keep roaches and
moths out and mealworms in), hinged lid at top of box, getting a tight fit of lid to keep
roaches out of your culture, and mealworms in.
E.....Place culture box inside, in an area of subdued light, away from
a wall or other thing that ants might crawl up in order to enter box.
2….Obtain a culture of mealworms from a pet store, a biological supply house, an
aquarium, or a zoo. If possible, get a mixed culture, containing all life stages from egg
to adult, so that you can quickly get larvae to feed out.
3….Put a 1-2" layer of chicken laying crumbles in the bottom of your culture
box as a food source for the mealworms. Add a water source for mealworms; source can be a
cut vegetable or fruit (apple, pear, orange, potato, banana, etc), or a sponge, rag, etc.
in a shallow dish (so laying crumbles do not get too moist and then moldy). Although other
food sources can be used, I found laying crumbles to be the best and easiest food to use.
4….Periodically check culture to see how mealworms are doing, to verify moisture
is still available, to add water to dishes at legs, to remove roaches, and to check for
ants.
5….After the culture becomes established enough for the numbers you want to feed
out, then you can start harvesting larvae (and adult beetles).
6….Just before the mealworms have turned the laying crumbles in fine debris and
excrement, add another 1" layer of laying crumbles for new food. Or you can add a cup
or two of crumbles weekly.
7….When the culture box gets fairly full you will need to remove part of the
debris, which also contains eggs and larvae, to the second box so you do not lose eggs and
larvae, and add laying crumbles to the space left by debris removal and to the second box.
After the second box gets well established, and then full of debris, you will periodically
need to discard some of the debris so boxes do not get too full. You can save some of the
larvae in the debris by putting the debris through a screen of suitable mesh size, or
putting the debris in a funnel with a light bulb above it. Larvae will try to avoid the
excessive heat of the bulb, will migrate down the debris, and drop out of the funnel into
a container placed under the funnel.
Problems:
---Keep legs of box in water containers to keep ants out of culture.
---Keep box lid tight to keep roaches and moths out of culture.
---Take boxes outside when you harvest mealworms IF you also have moths in the culture.
You do not want to let moths loose in your house, where they will attack various pet and
human foods, or clothes.
---Mites that may appear, which eat debris, etc., do not seem to harm the culture.
---Fruit flies can get established in the box if you use fruit or vegetable for moisture,
or the crumbles get too wet. These larvae or flies can be used as another food for your
animals, or can be discarded.
---Keep extra chicken laying crumbles in a fridge or freezer to avoid ant infestation and
moldy food.
---Make sure you do not harvest too many adults and thus decrease egg production.
---Over time, as debris increases, the waste products will emit an ammonia-like smell, and
part of the debris will need to be discarded.
---Boxes that get too full present short vertical distances for mealworms to crawl up to
lid, and make it more likely for them to escape through cracks around lid.
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