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Darkling Beetle Life Cycle

Batul Nafisa Baxamusa
The darkling beetle is a nocturnal insect that is found in the temperate regions of the world. The following article provides some information related to its life cycle.
The darkling beetle is a black-colored beetle with a round or elongated dome-shaped body. Adult beetles are metamorphosed from a larva. Its larva is known as mealworm, which is not actually a worm. Although it looks like a worm, it has six small jointed legs.

Scientific Classification

  • Kingdom:Animalia
  • Phylum:Arthropoda
  • Class:Insecta
  • Order:Coleoptera
  • Suborder:Polyphaga
  • Family:Tenebrionidae
  • Genus:Tenebrio
  • Species:T. molitor


The darkling beetle has hardened front wings called elytra. Thus, it is a flightless insect. Its antennae rise from under the ridge to near its eyes. These antennae have many segments that are enlarged near the tip. The head of the beetle is visible from the top and is followed by the pronotum and elytra.


This beetle is found almost all over the world and more commonly in temperate regions. Its habitat includes dark, cool places that are moist like under rocks, logs, etc. It is also found around chicken barns, grain houses, and animal burrows. The best way to get rid of a darkling beetle infestation is to coat the affected area with an insecticide that is allowed for use as per the law.


This insect feeds on fresh as well as decaying vegetation. It is a scavenger and eats grains and seedlings. It is considered as a pest due to its feeding habits. It eats all decomposing matter that includes dead plants and animals. It takes up water from the food that it eats.


If you are planning to raise this beetle, then you need to follow some basic care. You need to take a clear plastic cup with a lid. You can even use a cardboard box, aquarium tank, etc. Fill the cup with about 1/8" of wheat bran or crushed wheat flakes.
Then, place a crumpled piece of paper and a slice of apple or potato in it. Make sure that you replace the slice of apple or potato before it becomes moldy. Place the mealworm in the cup and cover it with the lid.
Remember to make holes in the lid. The mealworm will use the wheat bran, apple, and potato as food. It does not need water as it obtains water from the slice of apple or potato.

When handling the mealworm, use a plastic spoon to scoop it out. If you want to pick it up with your fingers, then use your thumb and forefinger.
Hold it at a side and gently squeeze it. It is generally very squirmy and wiggly, so you need to use a firm yet gentle grip. The larva will grow about 3 cm in size before pupating. By this time, it must have undergone molting 9-20 times.
The adult will emerge from the pupa after 2 to 3 weeks. In about 7 to 10 days, the female will lay eggs if there is a male beetle preset. After 14 days, the eggs hatch.

Life Cycle

The life cycle of this beetle is known as a complete metamorphosis. It undergoes 4 distinct stages. The female lays about 500 eggs in her lifetime. The eggs are extremely tiny, like a speck. After a few weeks, tiny larvae hatch from the eggs. These larvae are known as mealworms that are commonly found in pet shops.
The larvae are not really worms and are golden-yellow in color. They have 12 body segments and are similar to the caterpillar phase of butterflies. They have 6 legs in the front part of their body and all they do is eat and grow.
Like all members of their phylum, these beetles wear their skeleton outside their body. This is helpful protection against an attack by predators, but inconvenient while growing. Thus, the beetle undergoes molting of its shell periodically.
After molting, the soft, white larva expands and gradually develops a hardened shell. This process is repeated many times and by the end of the process, the larva grows about 2 cm long. After the final molt begins the pupal stage.
Unlike the larvae, the pupae do not eat or move and only twitch once or twice if disturbed. Inside the pupa, the mealworm turns into a beetle and in about 2 to 3 weeks, the pupa is split open.
The beetle that emerges is white in color. Gradually, the white beetle turns brown and after a day, it turns black. And just as any other creature, it mates, thus repeating the life cycle.
The darkling beetle is found all over the US and is one of the most popular classroom insects. It does not bite, fly, or release obnoxious smells, and is easy to care for. However, it tends to turn into a pest when feeding on new plants or stored grains.