As beekeepers we are all very aware of the 4 stages of a honeybee from egg to adult.

The Stages of Bee Development

1. Egg: The queen bee lays an egg, initially upright from the base of the cell. The egg hatches within three days.

2 Larva: Once the egg hatches, the larva emerges and is fed a special diet of royal jelly (for future queens) or worker bee food (for worker or drone bees). The larva grows rapidly and moults several times.

3. Pupa: After the larva has fully grown, it enters the pupal stage. This is where the cocoon comes into play. The larva spins its cocoon and transforms into a pupa. Inside the cocoon, the pupa undergoes dramatic changes as it develops into an adult bee.

4. Adult: After a period of 6 to 14 days (depending on the caste), the adult bee emerges from its cocoon. It chews its way out of the cell, ready to begin its role within the hive, whether as a worker, drone, or queen.

The Importance of the Cocoon in Metamorphosis

The cocoon plays a critical role in the process of metamorphosis. It shields the pupa from potential harm or disruption from environmental factors, predators, and disturbances inside the hive.

Although the cocoon material must be water-resistant, it also must protect the bee from drying, pathogens, and parasites. At the same time, it must be permeable to the gases of respiration, including oxygen, carbon dioxide, and water vapor.

 The protective nature of the cocoon allows the bee to undergo significant internal changes. Within the cocoon, the pupa’s body reorganizes as it transforms from a soft larva into a fully functional adult bee.  

The Structure and Composition of the Cocoon

“Silk” is a functional term used to describe protein fibres spun by honeybees and many kinds of insects and other invertebrate animals. The spinning of silk by honeybees does not involve either rotating or twisting fibres as is done in commercial fibre production but refers to the process of making an insoluble filament from an aqueous protein solution containing different fibrous and glue-like proteins.

In honeybees the silk comprises of 4 sub coils within a coiled single strand of silk and the newly spun cocoon looks like a cellophane sack. As the pupa progresses through the miracle of metamorphosis it gets bigger and hence the sack gets pressed into the cell wall.  Each time the cells is used to raise brood the cocoon remains after emerging, conveniently locking up the larva waste products which helps with hygiene, but inconveniently making the cell smaller internally each time.  Is there a correlation between old comb and smaller bees?

Social Hymenoptera insect (bees, hornets and ants) silk differs chemically from silkworm silk but performs the same principal function i.e. protecting the pupa.  Analysis of the mechanical properties of bee silk vs silkworm silk shows greater toughness and extensibility but reduced tensile strength which probably accounts for why we don’t use it as a luxury fabric.

Interesting, but so what?

The question remains – we know they exist, but have you ever seen a honeybee cocoon?

If you have good eyesight, you may sometimes see white/yellow tufts at the top or edge of cells particularly when clumsily removing unwanted queen cells and breaking into neighbouring sealed cells. Not ideal!

The best way to see cocoons is to melt away the wax from the comb leaving behind the cocoons, pollen, propolis and waste products. Honeybee silk remains stable up to 175C, well above the meting point of beeswax (62-64C) and that of steam(105C). Solar Wax Extractors and Easi-Steam enables the recovery of valuable wax to exchange for fresh foundation.

Written by Nigel Armstrong