The mouth parts are hidden inside a pointy protrusion between the two major palpates in the front.
In essence, the mouth parts consist of two dagger-shaped stylets that are actually transformed claws. When the stylets pierce the skin, they form a small tube. The tube may be inserted into the skin like a cannula. It does not go deep into the skin, only 10 -20 micrometers into the stratum corneum. This is the reason why fur mites cannot suck blood.
Saliva is injected into the skin through the small tube. When the enzyme-containing saliva has dissolved the tissue around the stylets, the mite retracts the stylets, thereby enabling the musculary pump of the throat to pump the dissolved tissue into the abdomen.