Detailed Guide to Mealworm Breeding Technology, Easily Master the Rearing Methods

Mealworms are holometabolous insects, meaning they go through four stages: adult, egg, larva and pupa. Adults have long, flat bodies, 1.4-1.8 cm long, dark brown with a metallic sheen, with a prognathous head, and the sides of the clypeus do not extend beyond the base of the antennae. During eclosion, the head, thorax and legs of the adult are light brown, while the abdomen and elytra are milky white; the newly emerged insect is soft and reluctant to move, and after 2-3 days the colour darkens, the elytra harden, and it becomes agile though unable to fly, crawling quite quickly. After careful feeding, the adult colony mates and lays eggs. Each time an adult lays 2-4 eggs, and each female lays about 300-600 eggs, scattered on the screen mesh at the bottom of the feed; the adult stage lasts about 60 days. The eggs are white and oval, about 1 mm in size. The egg stage lasts about 8-10 days; the larvae are brownish yellow, 2-3 cm long, with fairly distinct body segments, 3 pairs of thoracic legs, and a pair of tail projections on the 9th abdominal segment. When newly hatched the larvae are yellowish white, gradually turning brownish yellow, moulting on average once every 9 days, with each moult constituting one instar, for a total of 7 moults; after the final moult they pupate on the surface of the feed. The larval stage lasts about 60 days; the pupa is white, later turning white-yellow, with distinct body segments, and the pupal stage lasts 12-15 days.

Larva: Its appearance closely resembles wireworms and false wire beetles, with a slender body and a distinct clypeus, i.e. a clear suture between the labrum and the frons, and it is phytophagous. Newly hatched larvae are milky white, about 2 mm long, and thereafter moult, with each moult constituting one instar. They turn brownish yellow; fully grown larvae are 20-30 mm long, with distinct body segments, 3 pairs of thoracic legs, and a pair of tail projections on the 9th abdominal segment. Large larvae are 3-3.5 mm wide and weigh 0.13-0.24 g. At the final moult they pupate on the surface of the feed. The larval stage lasts about 50-70 days.

Pupa: The pupa just formed from the fully grown larva is milky white, with a soft body surface, very tender. Afterwards the body colour turns greyish white and the body surface hardens somewhat; it is a typical exarate pupa. The pupa is 15-20 mm long, about 3 mm wide, and weighs about 0.15-0.25 g each. There is a pale longitudinal stripe down the middle of the back, and the mouthparts are black. There are nipple-like projections on the sides of the abdomen (in male pupae the nipple-like projections are indistinct, with the base fused and the tip pointing backwards; in female pupae they are distinct, with a flattened tip, slightly keratinised, forked and markedly curved outwards). The thoracic segments are large, with rudimentary wings and appendages on the sides, and the head segment is also large, with a pair of black eye spots.

Adult: The first pair of wings of a newly eclosed adult is soft and white, then yellow, then yellowish brown, gradually turning black with a metallic sheen; the head is prognathous, and the sides of the clypeus do not extend beyond the base of the antennae. During eclosion, the head, thorax and legs of the adult are light brown, while the abdomen and elytra are milky white; the newly emerged insect is soft and reluctant to move, and the elytra turn black and harden, making it agile; the second pair of wings are membranous but cannot be used for flight due to degeneration, and it crawls very fast. After careful feeding, the adult colony mates and lays eggs; each time an adult lays 2-4 eggs, and each female lays about 300-600 eggs, scattered beneath the screen mesh at the bottom of the feed. The adult stage lasts about 30-90 days; adults resemble fireflies, with a body length of 10-18 mm and a width of 4-6 mm. Body weight is 0.1-0.2 g each, and the body is divided into three parts, head, thorax and abdomen, with 13 segments in total. The head has 1 segment, with a pair of antennae whose terminal 2-3 segments are enlarged and club-shaped, and the mouthparts are situated on the lower side of the head. The head is small and partly embedded in the prothorax, with a pair of black mandibles and chewing mouthparts. The thorax has 3 segments; there is no obvious dividing line between the pronotum and the pleuron, which are mostly fused, and the prothoracic sternopleural suture is distinct. The abdomen has 8 segments in total, with 5 visible abdominal segments and 1 segment at the tail. In males the intromittent organ is concealed within it, and in females the ovipositor is concealed within it.

Egg: Extremely small, milky white, long oval, with a long diameter of 0.7-1.2 mm and a short diameter of about 0.3-0.8 mm. The outer surface of the egg is the eggshell, the inner layer is the vitelline membrane, and the interior is filled with milky white egg contents. The egg stage lasts 8-10 days. At 25°C-32°C adults lay the most eggs and of the highest quality; below 15°C they rarely mate or lay eggs, and below 10°C they do not mate or lay eggs.