Tenebrio molitor is a darkling beetle whose larva, the mealworm, is the most widely farmed insect in Europe. It is used as feed for poultry, birds, reptiles and fish, and is authorised in the EU as a novel food.
1Life cycle
Like all beetles it undergoes complete metamorphosis: egg → larva → pupa → adult. Eggs hatch in one to two weeks. The larva moults 10–20 times over two to three months, then turns into a cream-coloured pupa. About one to three weeks later the adult emerges, first white and soft, darkening to black-brown within days.
Adults cannot fly well and do not bite. They live two to three months, during which a female lays several hundred eggs in the substrate.
2Rearing
Mealworms live in their food: a dry grain substrate serves as both bedding and diet, with slices of carrot or potato as the moisture source. Wheat bran is the classic choice, but oats do at least as well. In a 2025 feeding trial, larvae on oat flakes grew slightly more and converted feed more efficiently than larvae on wheat bran. See Mealworm substrate.
The ideal temperature is 25–28 °C. Cooling larvae to 8–12 °C pauses development, which is how live mealworms are stored.
3Nutrition
Dried larvae contain roughly 45–55 % protein and 25–35 % fat by dry weight, plus chitin from the exoskeleton. The calcium to phosphorus ratio is low, so for reptiles they are usually dusted with calcium before feeding.
4Research
Studies have shown that mealworm larvae can eat and partly break down polystyrene foam with the help of their gut bacteria. The work is still experimental, but it has made T. molitor a model organism in plastic-degradation research.