Tenebrio Molitor Basic Facts

jbaars edited this page Oct 7, 2014 · 1 revision

Home / Insect Species Guides / Mealworm Index / Tenebrio Molitor

Life cycle

The life cycle of meal worms can be divided into 4 stages, namely the egg, larva, pupa and beetle. The complete life cycle of meal worms varies from 19 to 31 weeks.

  • Eggs hatch into larva.
  • Larvae burrow below the surface of the grain and undergo a series of molts (10 to 20, average of 15), shedding their exoskeleton.
  • The last molt occurs about three months after the egg stage. Newly molted worms are white, and the exoskeleton has not hardened so they may be more digestible.
  • The fully grown larvae (worms) are golden brown and 0.98 to 1.38 inches (2.50 to 5 cm) long, with about 200 worms weight about an ounce (28.35 g).
  • The larvae come to the surface. They turn soft and plump, stop moving, curl into a "C" shape, and then transform into naked white pupae that turn yellowish brown after a day.
  • The pupae do not eat or move much.
  • Adult darkling beetle develops after 6 to 24 days (or more) from the pupae. At first, the beetle is white/light beige with a soft shell, and then it darkens and hardens to red, brown, and finally turns dark brown/black after about 2 to 7 days. The beetle is about a half to three quarters of an inch (1.25 to 1.90 cm) long. Males and females are visually indistinguishable.
  • Beetles lay their eggs 9 to 20 days after emergence. They lay for 2 or 3 months, and then die. Each female beetle lays about 275 tiny, bean-shaped white eggs - about 40 per day. The eggs are seldom seen because they are sticky and rapidly become coated in substrate.
  • Egg incubation takes 4 to 19 days (average of 12).
  • The cycle begins again as the eggs hatch into larvae, which may not be easy to see for several weeks. In 4 to 6 weeks they will be about 0.5 inches (1.25 cm) long.


Each female beetle can lay up to 500 eggs.

  • Source 1: The female deposits an average of 400-500 eggs that are bean shaped, sticky and white. The eggs are 1.7-1.8 mm in length and 0.6-0.7 mm in width. The time of incubation. is affected by temperature, the optimum being 2 weeks at 25 °C (Ghaly & Alkoaik 2009).
  • Source 2: 160 eggs/female (Oonincx and de Boer 2012).
  • Source 3: Beetles lay more eggs when the relative humidity is higher - ideally 70% (55-80% is good)” (Exotic Nutrition 2009).


The optimum incubation temperature is 25 ̊C - 27 ̊C, at which the embryonic development lasts 4 - 6 days (Larvae of mealworm (Tenebrio molitor L.) as European novel food 2013)

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