Growing your own mealworms is not complicated, but you will need some basic equipment. One plastic vivarium will be enough to start off with, but later, you will need another one or two as the colony expands. The quality of mealworms as a foodstuff depends on how well they are fed and cared for, so it is worth paying a bit extra for organic bran, porridge, potatoes etc. as you will be sure that they will not contain harmful insecticide residues.Equipment: Plastic vivatium tank with a ventilated top - the 12" wide and 8" high (31cm x 21cm) size is illustrated here.
This is a basic plastic tank - line it with some torn strips and pieces of newspaper, then cover with about an inch of organic bran, add a few more strips of paper, more bran, then layers of wheatgerm,, more bran and a topping of barley flakes or porridge oats. You need the substrate to be about 2-3 inches deep to start with - you will add more bran and porridge later, after it gets eaten by the larvae.
Push some short strips of paper down the sides of the tank to create shade along three sides. The layers of food and bedding are for your larvae to grow in after the adult beetles lay their eggs on the paper. Finally add some chunks of slightly dry bread (white or brown) and a potato cut into 4 or more bits to the top layer. The tank is now ready for your mealworm starter colony – these can be large mealworms, larvae or beetles. If you only have larvae to start with, do not add the potato until they hatch out into beetles, otherwise the bran will get damp and turn mouldy.
Mealworm, larva and newly hatched beetle on hand.
How often you need to add fresh potato (they also eat carrot and the beetles are very fond of apple) will depend on how many beetles and larvae are in the colony, as well as the temperature. Cold weather slows activity and very hot conditions brings on too rapid pupation of the mealworms, so don’t keep your tank near a hot radiator, or in a sunny position. I keep mine indoors and out of direct sunlight, but where I can easily check on them. As the oat flakes on the surface get eaten, sprinkle over another handful or so, plus oat or wheat germ. The fruit or veg will not need renewing more often than once every couple of weeks, unless you have a huge colony. Let them eat everything until only dry skins are left; if you add too much wet food the whole tank will get damp and unpleasant, so add less than you think they need until you get the balance right.
Beetles tucking in!
At first, you will not be able to see any sign of the newly hatched mealworms. The beetles lay eggs on the newspaper and dried crusts, which gradually get covered over as they burrow. The larvae are very small when they hatch out and they stay well down in the tank, eating their way through the foodstuffs and paper. Sometimes you can see where they are through the clear sides of the tank, as they move flakes of bran and grain aside. They are about the thickness of a single hair and only a few mm long, so you might need a magnifier to see one.
When the beetles start to die off, it’s time to move the survivors to a new tank, set up as before, to continue laying eggs to start another colony. The beetles can live for several months but a few die earlier and need to be removed. If you don't want want to start another tank colony to have a continuous supply of mealworms, scoop the beetles and vegetable skins out into a bowl with a large spoon and leave everything else in place – the larvae will eat everything as they grow larger, until finally, after 6-8 weeks, you will see small mealworms appear on the cut up vegetables. Keep on adding the bran and start adding quinoa flakes. These are high in protein and will boost the food value of the mealworms. The redundant beetles can be moved onto a compost heap where they will forage for food and provide a meal for passing hedgehogs.
Check the developing mealworms regularly by scooping up a spoonful of the bran mix to see how large they are. When they are the size you want, scoop out small amounts of the bran and shake gently in a coarse mesh plastic sieve, to separate out the mealworms. Put them into a smaller, ventilated container with some fresh bran, porrage oats and a small piece of carrot or potato. They should not be in a layer more than about an inch (2.5cm) deep to avoid suffocation.
At this stage it is worth sprinkling a calcium supplement into the small containers of mealworms, especially if you are feeding them to young birds, or parent birds feeding chicks. Mealworms are deficient in calcium and young mammals or chicks in captivity will need a good supplement of calcium, D3 and other vitamins and minerals, especially if they are on a mainly mealworm diet, to ensure their bones, eyes and feathers develop properly.
Hedgehogs like mealworms but if you could also spare some of the live beetles, it would be a great way for them to eat more naturally – in the wild a high proportion of their diet is made up of beetles.