close up of a group of mealworms on a white background

Understanding the Mealworm Life Cycle….The Essentials

Understand this and you will Produce Twice as Many Mealworms !

Once you understand the life cycle of the mealworm, keeping them will be a whole lot easier and you will be able to produce lots more. Mealworms are not worms as you may first expect, they are actually the larvae (immature stage) of the Darkling Beetle (Tenebrio molitor).

The darkling beetle has 4 main stages in their life cycle which takes around 3-5 months to complete depending on temperature, humidity and food availability. Each person will have a different set up, so don’t be surprised or disappointed if they don’t appear on the exact week you were expecting.

Life Cycle Summary

Adult beetles lay the eggs into a mealworms substrate which hatch into larvae (mealworms). The larvae grow and eventually transform into a pupae which is an intermediate stage between the immature stage (mealworm) and the adult stage (beetle). This is similar to a butterfly pupae. Once the beetles hatch they lay the eggs in the mealworm substrate and the cycle begins again.

Large mealworms eat small mealworms, and beetles eat everything from egg through to pupa. It is therefore important to separate all stages of the life cycle to prevent cannibalism and to maximize production.

The life cycle of the Darkling beetle takes approximately 3-6 months to complete depending on conditions. Below are the life cycle time frames:

  • Eggs – Once the beetle emerges from the pupa (cocoon) it takes approximately 2 weeks for them to mate and lay their first eggs.
  • Larva (mealworms) – Approximately 1-4 weeks after the eggs were laid, baby mealworms appear in the substrate.
  • Pupa (cocoon) – It can take anywhere from 7-10 weeks for the mealworms to develop to the pupa stage.
  • Beetle – It takes around 1-3 weeks for the pupa to develop to the beetle stage. Beetles live for around 2-4 months.

1) Eggs

  • It takes approximately two weeks for the adult beetle to mate and lay eggs after it emerges from the pupa (cocoon).
  • Each female beetle can lay 100-200 eggs at a time and up to 500 over their life. They lay the eggs into the mealworm substrate which is typically cereal or meal (ground up grain or seed).

2) Larva (Mealworms)

  • Once the eggs are laid it takes approximately 1-4 weeks for the mealworms to hatch and appear.
  • Newly hatched mealworms are tiny around 3mm long, white and have 6 legs and feelers. As they mature they change color to orange/brown.
  • To begin with they are only around 0.12 inches long (3mm), but quickly grow to around 1-1.5 inches (2.5-3.8cm). They require a lot of food and moisture at this stage, as they are preparing for the pupa stage.
  • Mealworms undergo around 10-20 molts, and appear white after coming out of the old skin.
  • It can take anywhere from 7-10 weeks for the mealworms to develop to the pupa stage.
  • Large mealworms will eat smaller mealworms so it is best to keep large and small mealworms separate.

3) Pupa (Cocoon)

  • The pupa is an intermediate stage between the mealworm (immature) and beetle stage (adult). The pupa looks like a white wiggly cocoon, similar to a butterfly pupa.
  • It takes around 1-3 weeks for the pupa to develop to the beetle stage.
  • The pupa does not require any food or a direct moisture (i.e. fruit or vegetables).
  • As the pupa eventually develop into a beetle which eat all other life stages including eggs, mealworms and pupa. For this reason beetles should always be separated.

4) Beetle (Adult Stage)

  • Beetles are the adult stage of the life cycle, and they lay the eggs in the mealworm substrate.
  • After emerging from the pupa, they will appear white, but quickly darken to have a black shiny shell. They have wings but will not fly away.
  • The adult feeds on cereal and meal and lives for around 2-4 months.
  • As beetles eat mealworms they should be removed from the container as soon as they appear and placed into a second container where they can lay their eggs into the mealworm substrate.
  • After around two weeks they mate and lay eggs into the substrate. Remember that the eggs are mixed in with the poo (frass) at the bottom of the container and this will provide you with the next generation, so don’t throw it all out.

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