What is the primary purpose of the rhythmic ticking or tapping sound made by the deathwatch beetle?

Answer

It is a function of the beetle’s mating ritual (stridulation)

The audible tapping sound is a form of sexual communication called stridulation, performed by the male beetle to attract receptive females ready to mate.

What is the primary purpose of the rhythmic ticking or tapping sound made by the deathwatch beetle?
attractioninsectwoodbeetlepest