Bee sting may have caused rider's crash

A bee sting may have contributed to the death of a motorcyclist in Perth at the weekend.

The 29-year-old man crashed into the centre island while riding in Forrestdale on Sunday afternoon.

An off-duty police officer started first aid before St John Ambulance officers took the man to hospital where he died.

Police believe the man had earlier been stung by a bee and started to feel unwell, but it was not known if the sting directly caused the crash.

Meanwhile, a 58-year-old motorcyclist died after his bike and a utility collided on a bend in Dardanup, in WA's South West region, on Sunday afternoon.