Lesson #1: Breeding basics
>> Here, you can learn about establishing an insect farm – including the choice of containers for mealworms and the composition of the breeding substrate.
The most commonly raised insect species for human consumption in our area is the mealworm, with its larval stage (worms) consumed shortly before pupation, or even the pupae themselves. The popularity of this species is primarily due to its excellent nutritional value and ease of breeding
Establishing an insect farm
Like most insect species, mealworms go through four developmental stages. Adult beetles lay eggs, from which larvae hatch after a few days. The larvae are quite active and feed on the substrate for several weeks, moulting their exoskeleton several times during that period (similar to snakes). After accumulating sufficient fat reserves for pupation, they shed their exoskeleton one last time and transform into pupae. Pupae do not consume food and are immobile, and approximately a week later, an adult beetle emerges from them. The adult beetles mature sexually after a few days, begin mating, and lay eggs in the substrate, repeating the cycle. Beetles are sexually active for about 8-10 weeks, and they die after a few more weeks.
Wikipedia: Mealworm (Tenebrio molitor)
The mealworm beetle goes through four developmental stages during its lifetime: egg, larva, pupa, and adult beetle
Breeding Conditions
The optimal temperature range for mealworm breeding is 25-31°C with a relative humidity of 50-75%. It’s a broad range, and even outside of these values, nothing catastrophic happens; it just slightly slows down the growth rate of the insects. Even at temperatures below 7°C, the mealworms become inactive, but it doesn’t harm them. Only temperatures below freezing and above 35°C are dangerous, potentially leading to developmental defects or increased mortality.
For completeness, here is the entire table of optimal temperature and humidity ranges for each developmental stage of the mealworm. The duration of each stage is only approximate and can vary significantly depending on breeding conditions.
Stage: —— Temperature ——- Humidity —– Duration
Egg: ———- 20-30°C ———— 55-75% RH ——- 7 days
Larva: ——– 25-29°C ———— 50-85% RH ——- 70 days
Pupa: ——— 26-30°C ———— 60-70% RH ——- 10 days
Beetle: ——- 26-28°C ———— 50-70% RH ——- 90 days
Mealworms will thrive exceptionally well in our climate in summer, but in the winter, it may be challenging to achieve optimal conditions indoors. However, the larvae generate heat (through enzymatic digestion of food). At lower temperatures, they form clusters in the substrate, and at the center of these clusters, the temperature can be up to 10°C warmer. This way, they self-regulate the temperature to their comfort. Lower humidity is not necessarily a problem; in fact, it helps control mold, mites, and diseases. However, it does require a more consistent supply of fluids through other means.
Rearing boxes
The most suitable material for rearing boxes is plastic. Mealworms can chew through cardboard or plastic bags, and they can climb on wood. Since you’ll be handling the boxes frequently, metal containers are suitable as long as they are not too heavy (e.g., gastronorm containers).
The container for mealworms can be of any shape, and a 5 cm high rim is sufficient so that you don’t have to chase escapees after filling it with substrate (about 2 cm in height). Ideal containers are solid food or euro crates that can be stacked. However, if you don’t have any on hand, you can use whatever you find at home. Purchasing standardized containers can be relatively expensive, but if you develop a liking for mealworm breeding and decide to expand later, you will likely have to invest in them.
Substrate
The basis of the mealworm’s diet is a grain-based substrate:
Wheat bran or bran, barley groats, oat flakes, soy or cornmeal, corn husks, ground dry bread (non-moldy), bran, etc.
However, in general, mealworms do not consume large, hard items, so whole, unground cereal grains will remain in the substrate, and you will have to sort them out later. Experienced breeders, therefore, prefer to always process the substrate through a grain crusher with a fine sieve.
The substrate is placed in the breeding box and is not changed during the feeding period, only if all of it is consumed, you can add new substrate or sift the box’s contents through a sorting sieve to collect the frass (insect faeces) and remove it.
Establishing an insect farm
Do you have the box and substrate ready? Let’s go shopping for the first mealworm generation!
The quickest purchase can be made at a local pet supply store. On the other hand, you can buy mealworms for starting your breeding project much cheaper online. To start your breeding, a package for a couple of € will be sufficient, and it will likely contain several thousand individuals. If you are not entirely sure whether you want or can manage the entire breeding process (pupation, hatching, and egg-laying) and you’d like to try feeding and consuming mealworms first, it’s ideal to get substrate with eggs. However, you need to be aware that the first movement of hatched mealworms is observable only after several weeks, and the first harvest will take around 2-3 months.
Place the box with mealworms in a darker corner or provide some shade. Mealworms like darkness.
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