Quasi-parallel bowshock structures are simulated by using a one-dimensional nonperiodic hybrid code in which the ion dynamics are treated exactly while the electron dynamics are omitted by neglecting the electron inertia (me=0) and pressure. The simulations are initialized with the upstream condition specified by &thgr;1=10¿, &bgr;1=0.5, and MA1 =2 to 4 with 0.5 increment while the downstream condition is obtained from the Rankine-Hugoniot relations, where &thgr;1 is the angle between the shock normal and the magnetic field, &bgr;1 is the ratio of kinetic to magnetic pressures, and MA1 is the Alfv¿n Mach number. The main results of our simulations follow: (1) For MA13, the magnetic field profile of the shock is turbulent. The upstream waves are again right-hand polarized whistlers with wavelengths varying from &lgr;~310 km upstream to &lgr;>1250 km downstream. The downstream waves are predominantly the right-hand polarized fast magnetosonic waves (&ohgr;≲&OHgr;i). (3) The transition from the laminar (subcritical) to the turbulent (supercritical) shock structures is shown to result from the firehose instability which occurs when MA1 >3. (4) The dissipation mechanism for the quasi-parallel shock in our simulation is identified with the nonadiabatic compression of ions streaming through the low frequency whistler waves (&ohgr;>&OHgr;i), resulting in conversion of ion streaming energy to ion thermal energy. (5) Significant ion heat flux flowing upstream occurs when MA1 >3 due primarily to the backscattering of highly nonadiabatically heated ions.