Summarize the following:
There are six types of hermit crabs available for sale in the United States. All of them are in the genus Coenobita.  The most common type out there is the Caribbean (Coenobita clypeatus,) which is also called "PP" for purple pincher due to, you guessed it, its large purple pincher. Wild Purple Pinchers are found in the Caribbean Islands. Most likely, when you see a hermit crab in a store, you will be seeing one of these guys. The Purple Pincher is the best one to start with because the others are more delicate and require much more detailed and intense care. The other types are Rugosus "Rug" or "Ruggy" (rugosus), Strawberry (perlatus), Ecuadorian or "E" (compressus), Cavipe or "Cav" (cavipes), Komurasaki "Viola" (violascens), Indonesian or "Indo" (brevimanus). Be patient with them when you first get your hermies--they will take a little time to adjust to their new home. When you get your hermit crabs, leave them in the cage for a few days. When you see that they don't hunch into their shell when you pass by then wait another day and try to hold your hermit crab. Let your hermit crab explore your hand and get used to you. Once you get them home, they go through a "De-stressing" period that can take as little as a few days and as long as two months. During this time, change out their food and water regularly and do not disturb them. Sometimes, even with the best efforts of even the most experienced crabber, hermit crabs can succumb to Post Purchase Stress (P.P.S.), and die. If your crab digs under the substrate for a couple of weeks, don't worry. As long as it doesn't stink like dead fish, he's OK. Please do not disturb your crab during this time. He will need to be alone and if he is bothered, the stress could kill him. Once in a while, a crab's exoskeleton gets a little tight, and like a snake shedding its skin, a crab will shed its exoskeleton and grow a little bit. Don't take the exoskeleton away from the crab! He will need to eat it in order to harden his new exoskeleton. If you have a sick crab, don't panic. Keep an isolation tank in a closet with enough substrate to dig under completely and ample food and water. If a crab is acting sick, he may be about to molt. This tank should also be kept with proper humidity and temperature as was mentioned previously. When hermit crabs grow, they need bigger shells. It is important to keep plenty of extra hermit crab shells similar to your crabs' sizes in the tank at all times. Once a month or so, rotate a few undisturbed shells out with different styles of shells.  Purple Pincher Hermit Crabs prefer the shells with round, circular openings.  They will choose circular openings over the oval openings. Ecuadorian Hermit Crabs will prefer an oval opening, because they have flatter abdomens. Never buy painted shells! Although companies may claim the paint is safe, the paint can chip off, and if the crabs eat it, it can be toxic. Most hermit crabs, when presented with a choice, will pick a "natural" shell over a painted one, even if it's not the right size. See the Warnings for information on what kinds of shells to avoid. Hermit crabs are scavengers by nature and will eat almost anything. Beware of commercial food, as it has many preservatives, such as copper sulfate, that may harm your little hermit. Don't feed them anything spicy, hot, or with preservatives in it.  Hermit crabs love silver sides and shrimp that are fresh, freeze-dried krill, blood worms, etc., and other seafood. You can normally buy these fishy foods at your local grocery store. If you cook, set aside a piece of steak or chicken, non-marinated to grill lightly for the crabs. They also eat raw meat. If you have more than twenty crabs or so, try getting a fish head from a local fish market. They are usually happy to give them away. You can put all of your crabs in a large tank or a large clean Rubbermaid storage container, (clear, no lid, or lid with VERY large holes cut in it) drop in the fish head, and a water-bowl, and leave them in there to eat for a few hours. You will mostly likely not want to do this very often, since the stench is pretty bad, but your crabs will love you for it! Aside from eating meat, hermit crabs also love different fruits and vegetables, among other scraps (they are scavengers after all.) Remember to change their food almost every day or night. Hermit crabs love to bury their uneaten food, and this can cause molding and is messy.  Hermit crabs love fresh fruit like pineapple, apple, pears, grapes, cantaloupe, watermelon, mango, papaya, strawberries, bananas, etc. Wash your fruit thoroughly before you cut it, to avoid pesticides. Crabs will go crazy for coconut shavings. Hermit crabs will also eat natural peanut butter on whole wheat toast, hard boiled eggs, egg shells (boiled), popcorn (plain, unsalted and unbuttered). Avoid anything from the Allium species of plants (onion, garlic, etc.). Some Hermit crabs love attention. When they are awake, carefully take them out of their crabitat. What do they like to do? Climb! Let them climb all over your shirt while you are watching TV or exercise them as they walk across both your hands (like a crab treadmill). It is important that they never fall, and are not out too long because they need humidity. Falling from a height of 3 feet (0.9 m). can be fatal for them, and fear of falling is the number one reason crabs pinch. Keep them in a position where they aren't going to fall and they likely won't pinch. Remember that they need humidity. Typical house humidity is only 40% and even less with AC and heat. When a crab's gills are exposed to low humidity it feels similar to how we feel when we hold our breath for too long. While they generally pinch only when they are afraid or feel cornered, they may pinch for no reason, so be prepared. Misting or running tap water on crabs to get them to release their grasp can hurt them and will likely result in them holding on longer and tighter. Please be very careful when handling them. You can avoid being pinched by holding your hand flat and tight so that the hermit crab will not have (as much) skin to pinch.
Know that there are different kinds of hermit crabs you can buy. Handle your hermies with care. Know that crabs go through molting and need extra shells. Provide shells for your hermie. Provide a steady and varied diet. Know what fruits and veggies hermies like. Play with them. Be aware that hermit crabs may pinch.