Mealworms have been used as a live food for pets for at least the last three centuries, the earliest accounts I can find on using meal worms as a livefood date back to the 1700's where they are used as a food source for caged birds such as nightingales. It is noted at what relative ease they are produced by simply having a tin containing some dry meal in the bottom (meal being crushed grain for making bread), a slightly damp rag placed on top of the meal for the beetles to reproduce on and it was possible to harvest enough mealworms from this crude set up to keep ones song birds happy.
Things have advanced in the production of mealworms now which is a huge industry and they are mass produced on a huge scale. If you wanted to have a go at breeding some mealworms yourself the theory is exactly the same as it was 300 years ago.
So what exactly are mealworms?, they are larvae, beetle larvae to be exact. Quite often people will assume they are maggots and no doubt if you have a pet that eats mealworms, visitors to your home will have shrieked at the site of them exclaiming how they detest maggots!. If you look closely you will see six little legs at the front of the mealworm, confirming its not really a worm at all. The beetle in question is the Darkling beetle and its latin name is Tenebrio Molitor.
How did they get the name mealworms? there is a hint to the answer above. They are a traditional pest species, a particular problem in days gone by for "meal" sacks, meal was not quite the highly refined baking flour we know today, it was a coarse flour, bran and crushed grain mix or just crushed grains. Stored in woven sacks in warehouses or on board ships, add a little bit of humidity into the mix and you have the perfect breeding ground for the Darkling Beetles.
The life cyle of the meal worm is temperature dependent, The colder the longer they take to go full circle and the warmer the faster. The ideal temperatures seem to sit between 20 to 25.c and at these temperatures they will take between 4 months to a year to complete the life cycle. The adult beetles will lay hundreds of tiny eggs on the substrate which is typically a layer of cereal based matter, there are usually receptacles placed on to the substrate for beetles to lay their eggs, this can be as simple as a damp cloth or a stack of cardboard egg crates. the latter being quite effective as the beetles will deposit their eggs securely in the tiny gaps around the cardboard. After around a week the eggs hatch and tiny mealworms 1 to 2mm in length will hatch out. These are eating machines, their sole purpose at this stage is to consume food and grow. This growth stage will take between 3 to 8 months and once the worms are around an inch in length they will pupate ready to change into the beetle.
Once in the Pupa stage they resemble tiny white aliens, they will stay like this for only a week if being kept at around 25.c but if cooler they can stay in the pupae stage for months. Finally they emerge from the pupa as light brown coloured adult beetles, darkening in colour as their shell hardens.