Ever since I started bringing home mantis, chameleons and other predatory species in order to take better pictures of them, I have had to breed Mealworms to feed them. Surprisingly enough they are very easy to rear and this is done with easy and the minimum amount of fuss.
The mealworm is not a worm; it is a larva. Any similarity to a true worm is incidental. mealworm larvae are golden yellow and have 13 segments—a head, three thoracic segments, and nine abdominal segments Mealworm larvae are the counterpart of the familiar caterpillar in the butterfly story. They pull themselves around on six stubby legs, one pair on each thoracic segment. Mealworms are the larval stage of Darkling (aka Tenebrio) beetles. Beetles, along with all their other insect kin (true bugs, flies, bees, wasps, ants, on and on), are members of the phylum Arthropoda, a word meaning jointed legs. Like all members of their phylum, insects wear their skeleton on the outside like a suit of armor. This is practical when they are under attack, but very inconvenient when they are trying to grow. Arthropods solved this problem by molting (shedding) this outer shell-like cuticle periodically. Immediately following the molt, the soft white larva expands before the new larger cuticle hardens. For mealworms this process repeats five times over a 2-month period, after which the larva is about 3 cm long. The final larval molt reveals the next stage, the pupa.
Life cycle Darkling beetles follow a life history known as complete metamorphosis. Like butterflies and moths, they go through four distinct stages during their life cycle. A female beetle lays eggs, as many as 500 in her brief lifetime of a month or two. The eggs are about the size of the period at the end of this sentence. After a couple of weeks the equally tiny larvae emerge from the eggs. The larvae are known as mealworms, but of course they are not true worms. The larvae are golden yellow and have 12 body segments. They are the counterpart of the familiar caterpillar in the butterfly story. Mealworms pull themselves around on six stubby legs that are all crowded at the front.
The larvae seem to have two purposes in life: eat and grow. Beetles are arthropods, and like all members of their phylum they wear their skeleton on the outside like a suit of armor. This is very practical when they are being attacked, but very inconvenient when they are trying to grow. The arthropods have solved this problem by shedding (molting) their shell periodically. Immediately following the molt the soft, white larvae expand before the new larger shell hardens. This process may repeat half a dozen or more times over a 3-month period, after which time the larvae are about 2 cm (3/4″) long. The final larval molt reveals the next stage, the pupa.
The pupae don’t eat and they don’t move except for a twitch or two when disturbed. Inside, however, the mealworm is turning into a beetle, much the same as a caterpillar turns into a butterfly while sequestered inside the chrysalis. In 2 or 3 weeks the pupa splits open and out walks a beetle, white at first, but soon turning to brown and finally black after a day. The beetles mate and lay eggs, and the cycle repeats.
The mealworm is not a worm; it is a larva. Any similarity to a true worm is incidental. mealworm larvae are golden yellow and have 13 segments—a head, three thoracic segments, and nine abdominal segments Mealworm larvae are the counterpart of the familiar caterpillar in the butterfly story. They pull themselves around on six stubby legs, one pair on each thoracic segment. Mealworms are the larval stage of Darkling (aka Tenebrio) beetles. Beetles, along with all their other insect kin (true bugs, flies, bees, wasps, ants, on and on), are members of the phylum Arthropoda, a word meaning jointed legs. Like all members of their phylum, insects wear their skeleton on the outside like a suit of armor. This is practical when they are under attack, but very inconvenient when they are trying to grow. Arthropods solved this problem by molting (shedding) this outer shell-like cuticle periodically. Immediately following the molt, the soft white larva expands before the new larger cuticle hardens. For mealworms this process repeats five times over a 2-month period, after which the larva is about 3 cm long. The final larval molt reveals the next stage, the pupa. 
Life cycle Darkling beetles follow a life history known as complete metamorphosis. Like butterflies and moths, they go through four distinct stages during their life cycle. A female beetle lays eggs, as many as 500 in her brief lifetime of a month or two. The eggs are about the size of the period at the end of this sentence. After a couple of weeks the equally tiny larvae emerge from the eggs. The larvae are known as mealworms, but of course they are not true worms. The larvae are golden yellow and have 12 body segments. They are the counterpart of the familiar caterpillar in the butterfly story. Mealworms pull themselves around on six stubby legs that are all crowded at the front. 
The larvae seem to have two purposes in life: eat and grow. Beetles are arthropods, and like all members of their phylum they wear their skeleton on the outside like a suit of armor. This is very practical when they are being attacked, but very inconvenient when they are trying to grow. The arthropods have solved this problem by shedding (molting) their shell periodically. Immediately following the molt the soft, white larvae expand before the new larger shell hardens. This process may repeat half a dozen or more times over a 3-month period, after which time the larvae are about 2 cm (3/4″) long. The final larval molt reveals the next stage, the pupa. 
The pupae don’t eat and they don’t move except for a twitch or two when disturbed. Inside, however, the mealworm is turning into a beetle, much the same as a caterpillar turns into a butterfly while sequestered inside the chrysalis. In 2 or 3 weeks the pupa splits open and out walks a beetle, white at first, but soon turning to brown and finally black after a day. The beetles mate and lay eggs, and the cycle repeats. 
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