I saw an excellent program on ticks on the a Discovery channel some months ago when they had a break in their regularly scheduled programming of overhauling motorcycle engines and documentaries on the Bermuda triangle.
They briefly went into the anatomy of ticks and their biting methods, but here’s the question (and the same applies to chiggers/mites):
Do they use the chelicerae just to scratch open a hole for the hypostome (nose/mouth), or do they also embed them in the hole? Just a guess is they are not used inside the hole, as the hypostome is barbed.
Does the tick/mite need to “inject” something in the wound (as the mosquito, who “spits” into the wound she makes) to keep the blood from coagulating?
Where does the “injection” come from? The chelicerae or the hypostome?
For ticks generally the whole structure is inserted. It’s rather like the alien in the Alien films, actually. The chelicerae form a sort of outer sheath around the hypostome when at rest - they tear a wound and then the mouthparts are thrust into the wound where the hypostome is exposed and used to anchor the tick ( some genera also secrete a cement-like saliva to help glue them in place on the wound ).
Mites lack hypostomes. For a few mites ( including chiggers ) the chelicerae will sometimes perform a dual function, with little hook-like structures on them helping to fasten the mite.
They don’t inject, so much as drool :).
Neither, exactly. The saliva glands produce anticoagulants, digestive fluids, and sometimes “anaesthetics” ( of course some species hurt like the dickens ). For Ixodid ( “hard” ) ticks, which typically attach for days, you’ll see a feeding pattern of sucking, followed by lengthy salivation, followed by sucking, etc., as a good blood pool is formed.