The evolution of collisionless, quasiparallel shocks (&thgr;Bn <45¿, where &thgr;Bn is the angle between the shock normal and the upstream magnetic field) is examined using two dimensional particle simulations. Reflected ions upstream from the shock are observed with average guiding center velocity and gyrational energy which agree well with the prediction of simple specular reflection. Strong ion heating through the shock ramp is apparently caused by large amplitude whistler turbulence. A flux of suprathermal electrons is also observed upstream with increased flux oblique to the magnetic field direction. Much stronger ion heating occurs in the shock than electron heating. The relevance of this work to the earth's bow shock is discussed.