Beetles undergo complete metamorphosis. That is, they progress through four distinct stages as they develop. These are: egg, larva, pupa and adult. Morphologically, the larval stage is not similar to the adult stage. A summary of each of the different stages follows below.

Egg: The eggs develop inside of the female beetle and are laid in large numbers or individually.  In a few days the eggs hatch and the young are born.  In most cases the female beetle does not provide any sort of maternal care for the young, with the young being left to fend for themselves.  The eggs are generally laid near or on an appropriate larval food source.
Larva: Upon hatching the wormlike larva begins to feed.  As the larva grows larger it passes through a number of stages or  instars.  Each of these instars ends with the larva molting to accommodate its growth.  Depending on the species the number of molts can range from as few as three to many.  The bodies of  beetle larva take on numerous diverse forms.  The most common ones are C-shaped, wormlike, wirewormlike, caterpillarlike and campodeiform.
Pupa: Upon reaching the final instar the larva transforms into the pupa stage.  This stage serves as a transition period during which the larva becomes an adult.  The pupa is typically pale in color with the appendages being unrestrained and distinguishable.
Adult: The final stage of development is achieved when the pupa molts.  The newly emerged adult beetle is teneral - the exoskeleton is soft and with pale coloration.  Typically, it takes several hours before the body hardens and adult coloration is present.

Ladybug Metamorphosis

Darkling Beetle Metamorphosis