The lifecycle of hermit crabs can be quite a complex process and one that is perilous for the crab especially during hatching. So if you are looking to breed your own hermies successfully in captivity, then it might be beneficial for you to discover what happens during the early stages of a hermie's life cycle.
It is important to note that there are two types of hermies available; those which live in the sea, and those which live on land! Although the majority of the species live in the sea, the land species are the ones that the majority of people keep as pets. Therefore I am going to concentrate upon these. Another important factor to take into consideration is that all hermies, no matter whether they are sea or terrestrial types, are born in the water.
The first stage of the life of one of these crawly critters is the mating stage. The male crab has to approach the female and encourage her to exit her shell. He does this by gently knocking on the female shell and enticing her out. Once this is achieved, the male places his spermatophores into the females gonophores and fertilizes the eggs which are stored there. Once this process is complete the female will carry them around in her underbelly within the confines of her shell. This keeps the eggs not only safe from predators, but also keeps them moist.
When the eggs are due to be hatched, the female makes her way to the shoreline and empties her eggs onto the sand or rocks. It is here that the waves will carry them into the sea. This is where the life of the little critter really gets interesting and somewhat dangerous.
When the tiny hermies are hatched they are known as "zoea". They spend the first few weeks swimming around the ocean, whereby the ocean currents can send them miles off course, as part of the plankton. At this stage they are incredibly vulnerable and will easily fall prey to larger sea creatures who have a taste for plankton.
After a few months and many changes of skin, the living conditions of the hermie alter again. This time the tiny zoea begin to resemble what is more like the crab that we know and love today. Those that have survived this far have now developed into "Glaucothoe" These are tiny crabs that can now walk about as well as swim. They remain in the ocean but are still vulnerable to predators because they at this stage have no protective shell. They are in a race against time to find a shell that will offer them protection, as well as comfort, for the perilous journey back onto land. If a glaucothoe tries to make it back on to land without the aid a protective shell, then the chances of it surviving are pretty minimal.
Having successfully avoided all the pitfalls, the baby hermie eventually makes his/her home further from the shoreline where it will live nocturnally, scavenging for whatever food it may find. After several more moltings and around two years in length, the hermie reaches adulthood. It is only then that it can start to breed again and therefore can continue the intresting lifecycle of hermit crabs!