Dufour’s Gland Creates Waterproof Nest Linings

honeybee perched on purple flower in close up photograph during the day

Biological Strategy

Cellophane bee

Holly Kerstiens

Image: Dustin Humes / Unsplash / Free non-commercial use

Chemically Assemble Organic Compounds

Part of the reason that synthesis reactions (chemical assembly) can occur under such mild conditions as ambient temperature and pressure in water is because most often, they occur in a stepwise, enzyme-mediated fashion, sipping or releasing small amounts of energy at each step. For example, the synthesis of glucose from carbon dioxide in the Calvin cycle is a 15-step process, each step regulated by a different enzyme.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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The Dufour’s Gland of bees secretes a multitude of organic compounds like polyesters for nest building, triglycerides for food and hormones for communication.

Dufour’s is a small gland near the stinger of a bee. It’s an exocrine gland, secreting chemicals, but the purpose of the chemicals and their structure differs from family to family. The secretions can be used for anything from nest building, to reproduction, to pheromones, to the production of larval food. Dufour’s Gland is not unique to bees, being found in many different insects.

Dufour’s Gland can produce a variety of organic compounds, including both saturated and unsaturated hydrocarbons, with long chain hydrocarbons being the most common secretion across bee taxa. More volatile and non-volatile compounds are produced by certain bees, including alcohols, s, aromatics and fatty acids.

The most common Dufour’s Gland secretion among bees is used to create a waterproof lining for their brood cells, protecting the stashes of food they leave for their larvae, as well as the larvae themselves, from microbes or environmental conditions. The polyester brood cell lining has qualities much like those of cellophane. In the bee genus Colletes, the lining is made up of 18-hydroxyoctadecanoic acid and 20-hydroxy-eicosanoic acid, both stored as lactones in the gland before they are secreted and undergo a chemical reaction to become the lining.

The larvae may also ingest secretions from Dufour’s Gland with their food. In Anthophora abrupta, the secretions are made up of a mixture of liquid triglycerides, one long-chain fatty acid and two short-chain fatty acids before they’re added to the food.

Dufour’s Gland secretions are also often applied to the entrance of the nest, being unique enough to each individual that they serve as a marker for which nest is their own.

In the Andrena genus the compounds produced by the gland vary based on genetics, implying they may play a role in recognizing kin. In some bees, such as the stingless Meliponini bees, the secretions of a virgin female and a non-virgin female differed by the inclusion of an ester compound, implying they could be used for sexual signalling.

In bumblebees (genus Bombus), Dufour’s Gland increases in size with age and reproductive activity of the Queen, while in workers Dufour’s Gland advertises their sterile status using esters. When an individual develops ovaries, the esters are no longer secreted.

This information is also available from the University of Calgary Invertebrate collection, where it was curated as part of a study on design inspired by bees.

Last Updated April 3, 2019

References

“Ground dwelling bees face the challenge of keeping their larval food free from microbial growth, desiccation, and soaking by water. They have evolved to respond to this challenge by coating their brood cell with a hydrophobic lining that forms a sheath around the larval food. Secretions of the Dufour’s gland have been found to be involved in forming this cell lining.” Mitra, 2013.

“Mated queens had higher proportion of macrocyclic lactones (used in nest construction), and lower proportion of isopentyl esters (volatiles), as compared to virgin queens, and the composition of Dufour’s gland compounds was found to change within one day of mating (Ayasse et al. 1993). In the same species,Lasioglossum malachurum (Halictidae), the pattern of ester composition has also been found to differ between young virgin queens and old nesting queens, and the pattern has also been correlated with volume of fat body and status of ovarian development, implying possible involvement in sex pheromonal communication and in nest recognition”Mitra, 2013.

Journal article