Why are there so many holes in a Mosquito? What are they for? Surely they will cause drag?

A look at what the apertures, ducts, ports and intakes are for on a Mosquito. The high performance of the DH.98 Mosquito was partly due to it’s light-weight composite construction, mainly built of different types of wood.Another factor was the smooth aerodynamic shape of the fuselage and wing, making the aircraft very “slippery” and reducing drag. To help still further, the fuselage and wings were also covered with fabric, which was doped over the plywood skin, to make the airframe even smoother.
But the aircraft was not perfectly smooth. There are all sorts of lumps, bumps and holes scattered over the plan. These must all be creating some sort of parasitic drag. So what are they, and why are they there? That’s the purpose of this video.