Bombykol: The First Pheromone Ever Identified

Every Pheromone Story Starts Here

Bombykol, isolated from the silkworm moth, was the first pheromone ever chemically identified in any species. Adolf Butenandt and his colleagues at the Max Planck Institute of Biochemistry in Munich published the structure in 1959 and synthesised it.

Before that, chemical communication between animals was inferred and argued about. After it, it was a molecule with a formula.

What It Took

The detail that stays with people: Butenandt purified bombykol from extracts taken from more than five hundred thousand moths.

Half a million animals, to isolate enough of a compound to determine its structure. That is the scale early natural-product chemistry operated at, and it is a large part of why the work took years.

The Molecule

Bombykol is (E,Z)-10,12-hexadecadien-1-ol. The E and Z matter enormously: they specify the geometry at two double bonds, and the moth's response depends on getting that geometry exactly right. A molecule with the same atoms in a different arrangement does not work.

How the Moth Detects It

The female releases it; the male detects it on his antennae, in structures called olfactory sensilla, with a specificity and sensitivity that is the reason moth antennae look the way they do — feathered, to maximise surface area.

The receptor itself has since been identified: BmOR-1, a gene sitting on the Z sex chromosome, expressed only in males, and only in the pheromone receptor neurons of the antenna, switching on in the late pupal and adult stages. The animal builds the detector just in time to need it.

Why a Silkworm

The same reasons as always. Butenandt needed half a million moths of one species, of known sex, at a known life stage, all at once. There was exactly one insect on earth that could be supplied like that — because an industry had been rearing it in millions for thousands of years.

The discovery of pheromones required an animal that was already farmed.

Related: the wild ancestor · the silkworm genome