In this age of the internet, we need no reminder that animals are obsessive communicators. They employ a variety of media to convey their messages, smell being the oldest and most pervasive of them all. Smell, or chemical signalling, has the advantage that it can propagate over a long distance, going round all sorts of barriers. It can also be highly specific, taking advantage of the great variety of signalling molecules that animals can elaborate.

Silkworms have the distinction of being the first animal for which the chemical signal was deciphered. This is a chemical produced by the female from an abdominal gland, a single molecule of which is sufficient to set off a response in the male. So males fly towards the female from hundreds of metres homing in on increasing concentrations of the signalling chemical. Once close by they too must produce another distinctive chemical which the female needs to smell to agree to receive them. Bonding chemically is about all that the silkworms do as moths, having relegated all feeding and growing to the caterpillar stage.