Mealworms are the beetle species Tenebrio molitor L., which are commercially farmed as a source of food for pets, and in some cases, humans. The mealworm is the larval stage of the beetle, which is commonly used by wildlife rehabilitation centers, zoos, and pet owners to feed an assortment of animals ranging from bats and birds to lizards and geckos to name a few. Fish owners and fishermen also use mealworms as food or bait, respectively. The mealworms are most often used live in these cases, although frozen worms can also be used. Mealworms are also approved for use as human food in some countries where they can be cooked and eaten as whole insects or ground into flour and used in various recipes.
The Nutritional Composition of Mealworms
Mealworms are 3.2% ash on a dry matter basis and are high in many nutrients; for instance, they contain large amounts of protein and fat, with quantities varying depending on their diet. The fat is mainly in the form of healthy polyunsaturated fatty acids. The mealworms also contain magnesium and zinc and most of the B vitamins, including B2, B3, B6, B9, and B12. They are, however, somewhat limited in calcium content but do provide many of the required essential amino acids. When it comes to feed efficiency, mealworms can convert up to 45% of the protein in their diet into edible body mass, making them a good source of nutrition. In general, mealworms are believed to be an excellent source of nutrients, and some believe even richer in nutrients than traditional livestock.
Life Cycle Stages
Since mealworms are beetles, they have a holometabolous or complete development; they have an egg, larval, pupa, and adult stage. The stage of development most commonly used as food is the larval stage, when the beetles resemble worms. The life cycle takes an average of three months, with some variation in duration depending on temperature. The adult beetle lays around 500 eggs in her lifespan on the substrate; these eggs take 10 to 12 days to hatch. The larvae pass through several stages called instars, and within 8-10 weeks, they pupate. The pupa takes 12 to 20 days to change into the adult beetle. Adults mate and lay eggs, and they survive up to 3 months.
The exact length of stages depends on temperature, food, and moisture availability. Development time is quickest at 30°C and longest at 17°C, and they do well at a humidity of about 70%. Too high temperatures can quickly kill the mealworms; they can survive at fairly low temperatures in a refrigerator but will not develop into the next stage. Mealworms can carry certain parasites in the wild, which impacts their survival. The larvae also need to be kept at a density below 96 worms per 120 cm; at the higher densities, the biomass per gram of feed drops by 22%.
How to Breed Mealworms?
Diet and Water Requirements for Edible Mealworms
In general, the growth and development of mealworms are best when they are fed mainly on carbohydrates (at least 80% to 85% of the diet is a carbohydrate). Mealworms can be reared easily on wheat bran and dry oatmeal; these can also be used as the substrate. For a source of water and added nutrients, vegetables such as carrots, pieces of potato, spinach, lettuce, and pumpkin, can be added. Fruit like apples can be used in minimal amounts and should be removed quickly due to rapid mold development. Care must be taken not to add too many fruits or vegetables and to remove uneaten and old food after one or two days because the development of mold would prove fatal for the colony.
The presence of at least some vegetables or fruit is necessary, and the worms will not survive if this is not provided in addition to the wheat bran or oats. Besides moisture, many green vegetables will provide B vitamins, another nutrient that helps increase the growth rate of mealworms. The feed conversion ratio of mealworms varies from 2.62 to 6.05 based on fresh weight. However, protein content only varies about 3% of dry matter and ranges from 45% to 48%. Fat content ranges from 19% to 28%, with higher values achieved if their diet is higher in protein.
Indoor or Outdoor Farming?
While mealworms can be farmed outside, there are challenges, including the increased likelihood of the colony becoming infested by rodents. Thus, your colony would be decimated unless carefully protected and sealed from invasion by other animals. Weather changes would also have an effect, and if you live in a cold climate, growth, and development would be too slow to make an outdoor farm productive.
Indoors, temperature and humidity can be carefully controlled for optimal development and survival. Possible vermin, including rats, mice, and cockroaches, can be more easily excluded and prevented from infesting colonies where mealworms are housed and maintained indoors.
Containers and Setting up the Colony
Mealworms can be cultivated in plastic containers that are 60 cm x 40 cm x 12 cm. Using cardboard as a container is inadvisable because the worms can simply chew through and escape. It is essential to remove pupae and place these in a separate container to avoid cannibalism of pupae by the larval stage.
Once adults emerge, they will start to mate and lay eggs. Once the eggs hatch, larvae need to be removed and placed in a separate container. There need to be separate containers for larva, pupa, and adult stages because of cannibalism. This means that containers need to be searched often in order to remove and separate different stages of development.
Mealworm larvae should be harvested once they reach the largest size; they are removed and separated from any excrement and substrate and then immediately frozen by placing them in a container and freezing for 48 hours below -21°C. Blanching is the next step and is important in order to reduce microbial contamination of mealworms. Blanching involves boiling the mealworms at 100°C for at least 40 seconds. After this step, the following process is drying.
Different drying processes can be used, all of which are similar in terms of the resulting nutrient content of the mealworms:
- worms can be freeze-dried by placing them in a freeze dryer for 24 hours at a temperature of -50°C;
- worms can be dried in a vacuum oven for 24 hours at a temperature of 60°C;
- use a rotating rack oven for 1 hour and at a temperature of 120°C to process frozen worm;
To process the worms into flour, they are put through a grinder, using, for instance, roller mills, and then larger parts sieved out. The result should be a fine mealworm powder or flour.
Monitor, Manage, and Forecast
Now you know the main points on how to breed mealworms, but as a mealworm producer, you must identify discrepancies before any issue arises. By controlling all the critical points such as temperature, the right amount of light, humidity, feed type, cycle speed, conversions, densities, the nutritional composition, you can avoid the loss of the colony.
Manual data collection and analysis take time. Information stored in different places does not talk to each other, or you need to have specific knowledge to read it. Cogastro software helps farms track all the required variables and provides real-time estimates of yield, cycle speed, feed conversion rate, hatch rate, and other vital metrics.