Maintaining a mealworm colony is simple – try it as a pet, for a school project or just for fun!
Food & water
Mealworms have very simple tastes in food. The best part is, their food doubles as their bedding. Simply line the mealworms’ home with any dry grain or cereal, like rolled oats or bran. Make sure the surface of the bedding is at least 4 cm from the lip of the container. Like any living thing, mealworms need something to drink. A little dish of water won’t do it, though – mealworms need to get their water from something solid, like a vegetable. Put slices of carrot, celery, potato or green pepper (or any other fruit or vegetable) on top of their bedding. Choose a vegetable that won’t go mouldy too quickly, and exchange the pieces for fresh slices every 5-7 days. Vegetable scraps work well – try using the ends of celery or carrots that would have been composted otherwise.
House your mealworms in a container at least 8 cm deep and made of a smooth material; glass, plastic or metal work well. Mealworms can climb cardboard and fabric and so will escape from containers made from anything they can grip. The beetles can’t fly, so the containers don’t need lids. If you decide to use a lid to avoid spilling, be sure to provide air holes!
Caring for life stages
Mealworms start out life as an egg, then hatch into a larva, morph into a pupa, and finally emerge as a beetle. (Read all about their life cycle in the ‘Mealworm Life‘ section). Both the beetles and larvae will eat the immobile pupae, so it’s important to keep the life stages separate. When you spot any pupae lying on top of the bedding, take them out and store them in a container lined with paper towel. They don’t need food because they don’t eat during this stage. Cover them with more paper towel in case they emerge upside down and need something to grip. You can store the beetles either in their own container or in the same container as the larvae. It’s ideal to store each life stage separately, but it’s a lot more work.
Every so often you will need to remove the mealworms’ waste. Their poop looks sandy and will collect at the bottom of their container. It’s easy to remove by pouring everything into a sieve; the poop will fall through. Because mealworm eggs are quite small, most of them will also fall through. If you’re interesting in maintaining a colony, keep the sifted poop in ‘quarantine’ with some added food and vegetable until the larvae are big enough to scoop out.
If you decide to harvest larvae for food (either for you or for a pet), wait until they’re nice and big. Separate them from their bedding either by sifting them through a sieve or by picking them out one by one. Mealworms like climbing screen-type material, so even if all of their bedding doesn’t fall through the seive, wait a few minutes for them to start climbing, and then lift them out with a spoon.
Although some people would consider mealworms themselves to be pests, there are a few other creatures that can interfere with your thriving colony.
These are small, grey, triangular-shaped moths. Their larvae look like little white inchworms and spin a web in the bedding. You’ll know if you have this infestation because you’ll see moths fluttering around, and you’ll find webs in the bedding. These moths don’t eat fabric, but they can infest your own food, so make sure your kitchen grains and cereals are sealed tightly. To get rid of them, set out meal moth traps (pheremone-based glue traps available in most hardware stores) and kill any adult moths you find. The moth larvae are very difficult to find in the mealworm bedding, but if you find any, remove them right away. Be sure to kill them, because unlike mealworms, they have sticky feet and can climb out of anything.
Mould is often caused by too much humidity in your container. If you find mould growing, try using a drier vegetable as your water source. Leave the top slightly ajar to let air flow through. Finally, get rid of any obvious mould you see and replace it with fresh bedding.