If you have ever been bitten by a mosquito, you have experienced an haustellum at work, preparing to suck your blood. Interestingly, this is not a tube, but three tightly spaced hairlike structures, of which one is sensory, and two are alternate protrusible spikes to penetrate skin. Close proximity of the three structures makes capillary attraction cause blood to rise up them.

PS If you hate gettung bitten or stung, you are a cnidophobe. There are a lot of us.