Alan W. Harvey (from the Department of Biology at Georgia Southern University) wrote:
“Sexing land hermit crabs out of the shell is straightforward. Females have well-developed pleopods (the small legs) on on the left side of the abdomen, and a gonopore (an opening through which eggs or sperm are released) at the base of the second pair of walking legs. Pleopods are absent or at best vestigial (small) in males, and the coxae of the last pair of legs are, in most species, produced into stout, somewhat tubular structures (the legs have a wide, tubular look to them).”
Note: The information in brackets was added later by me to help de-mystify the technical words.
Also, Jones, S. and Morgan, G.J. (1994) said of Coenobita
Males and females differ only in the position of the gonopores
[ Glossary ]
BREEDING LAND HERMIT CRABS
It was always thought that hermit crabs would not breed in captivity. Now, it seems, some have successfully bred with suitable conditions. While we are still working out what they are, it is obvious to all that if the hermit crabs are given enough room to move about in; both a fresh water bowl and a salt water pond; a balanced diet including carrion-type foods high in protein and calcium; humidity and temperature in the ideal range; and enough shells for growing and fussy bodies. While we are not sure what makes some hermit crabs breed and others not, it is important that their home meets all their needs, and yields a better chance of survival.
While hermit crabs have successfully bred, it is much harder to successfully hatch and raise the land hermit crabs. Since the first stage of development of land hermit crabs is an aquatic one, the eggs will need to be released into, or placed in, an aquatic environment to simulate the time spent in intertidal pools as part of plankton. Read about their lifecycle for more details.
Unless you have the time and ability to raise the zoea to juvenile (air-breathing) stages, there is little chance they will survive. At each stage of development within the aquatic stage, the zoea (free swimming larvae) need to be fed by hand and kept in conditions which may be difficult for most. However, if you are able to raise land hermit crabs to juvenile stage, there is a good chance that the health of these offspring will be optimal, depending on feeding and conditions.
You can read an article by Stu Wools-Cobb on The Crab Street Journal – someone who has successfully bred and raised land hermit crab within his home.
A hermit crab that is gravid (carrying eggs) will look like the drawing by Alcock, below. “A female crab attaches her eggs to the fine setae on her pleopods using a gluelike substance.” (Fox, S. 2000)
Harvey, A. Text from a personal email regarding determining the gender of a land hermit crab. Shared with permission. For more information about Alan Harvey and his research, please visit the link below
Jones, S. and Morgan, G.J. (1994) A Field Guide to Crustaceans of Australian Waters. Western Australian Museum. Chatswood, N.S.W. (Australia) : Reed Books, 1994. ISBN 0 7301 0403 6
Lowry, J.K. (1999 onwards). ‘Crustacea, the Higher Taxa: Description, Identification, and Information Retrieval.’ Version: 2 October 1999. http://crustacea.net/