Culturing Mealworm
Text & Images by Paul Barrow
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Mealworm (Tenebrio molitor)
Mealworm is an excellent food for birds, reptiles and fish of all sizes. They are highly nutritious, clean, dry and disease free, everything needed to maintain healthy fish. Mealworm are the larvae of the Mealworm Beetle, Teberio molitor , which completes it whole of its lifecycle eating the milled flour made by us. They are so successful in their pilfering ways that they have a marked outcome on the economies of some counties. Like most of the order Coleoptera (Beetles), they go through a 4-stage lifecycle: egg, larvae, pupae and beetle.
The Eggs
Don’t bother looking you won’t find these minute objects.
The Larvae
The larvae of these beetles grow to just over 2.5 cms, and resemble a hard-shelled caterpillar. They have a distinct, dark head and a long brown body with two rows of 3 legs at the front. Their lifecycle from egg to sexually mature beetle is about 60-days, however the different stages in the lifecycle are highly variable, potentially increasing this time  up to 5 months. By far the longest of these  stages is, fortunately for us, the  larval  stage, which can last from 2 weeks to a few months. 





 The Pupae
These are strange, pale squat things that appear dead until touched when the tail end rotates vigorously.





The Beetles
They are small, less then 2cms, matt black creatures very much like the Ground Beetle found in the garden but, unlike their garden cousins, they do not bite and are not aggressive.







Culturing
Culturing these creatures could not be simpler, a large plastic or glass container about 25 x 20 x 20cms, filled nearly to the top with bran or oatmeal and covered with a fine mesh net will produce a good supply of mealworm for a year or more. Add to this a tub of shop bought mealworm, first removing any dead ones. Leave the container in a warm, dry place for nature to take affect, and within less than a week the first beetles will appear. Newly emerged beetles are very pale and go through darkening stages of brown until fully black. Once the beetles are black it could take as little a 4 days for first eggs to hatch into minute larvae. The larvae grow rapidly and need to split out of their shells 10 or more times to maintain this growth. During the last split, they turn into pupae instead of continuing as larvae. A fully functioning community of mealworm will produce a variety of sizes, and can be used for most sizes of fish once sorted. When the worms split form their shells they are soft, white and suitable for fish with the tenderest of tastes. Don’t feed the beetles or pupae, as they will produce the next generation. You will not get your mealworm to grow as big as those in the shops because their growth rate was artificially slowed to make them grow bigger. Mealworm float because of their dry environment, so if you want to feed them to catfish, place an apple or potato slice on top of the bran for a few days, the extra moisture makes the worms sink.

Giant Mealworm (Zophobas morio)
This a species of Darkling Beetle, which also includes the Mealworm Beetle. The larvae of this beetle are known as the Giant Mealworm or Superworm (5-6cms) and were introduce to the hobby in the mid 1980s. These South American beetles are similar to the mealworm commonly fed to reptiles, fish & birds but need to be maintained at a much narrow temperature range of 70 to 80 degrees. They can be kept in a variety of substrates but bran seems to be the easiest if they are not to be bred. In fact, they are not easy to cultivate because they can stay in their larval state for a very long time. Unlike mealworms, giant mealworms need moisture or they will die or cannibalize their brethren. A simple answer to this problem is to feed them apple, potato or greens. They are highly nutritious, with a much lower chitin (hard exoskeleton) content than ordinary mealworms.