Common name: Dubbed 'Blueberry' by Felix Wang
Distribution: Riau Islands and Kalimantan/Borneo coasts, Japan (Ryukyu Islands), Singapore, Taiwan, Eastern Malaysia, and Indonesia
Habitat: Live in the forest near the coast but can be found in the beach during beginning of summer and autumn.
Characteristics: Coenobita purpureus (colloquially referred to as the purple land hermit crab) is a species of land hermit crab native to Japan. Dubbed 'Blueberry' crabs by Felix Wang. Their coloration is usually purple, blue, purple-blue, or purple-red although as young crabs they are colored white. Their eyestalks are long and their eyes are oval in shape. The joints of their pincers and walking legs are yellow and the abdomen is short and fat. They can be 17mm in length. They live in the forest near the coast and can be found near the beach in the beginning of summer and in autumn.
Other sites indicate this species is threatened but that seems to be untrue: 'The information on Wikipedia page about C.purpureus is also incorrect - since they never did any research about this species. This species is not threatened ( can still abundantly found in Riau Islands and Kalimantan/Borneo coasts ), and not only native to Japan (Ryukyu Islands); otherwise it is also native to Singapore, Taiwan, Eastern Malaysia, and Indonesia as well.' 1
Body colour can be from light blue to dark purple. Most of them are Purple-blue, Purple, Blue and Purple-Red etc. They were in white colour when they are juvenile, and will become blue or purple when they grow up. Eyes are elongated in shape and there are a yellow stripes surround the eyes (Black arrow) . Eyestalks are white / light yellow in colour. Generally, there is no black-brown stripes on the eyestalks (Red circle) but there are also some exceptional case Tips of the 1st pair of antenna (Red circle) is red. The bottom of the 2nd pair of antenna is white in colour. Antennal acicle cannot move, fused with second segment of its peduncle. Left claw is larger than right claw. There are 4~5 ridge (////) on the upper part of the big claw (Red circle). There are some hair on the inside part of both claws. The joint of claw is yellow in colour and have filiform red colour on the joint. The joint of walking legs is also yellow in colour and have filiform red colour on the joint (Red circle). The last 2nd part (dactylus & propodus) of their 3rd left Walking legs is not flat. According to the articles of Akira Asakura (Japan Natural History Museum and Institute, Chiba) and Yukio Nakasone (University of the Ryukyus), outer surface of propodus of left 3rd leg separated from dorsal surface by a well-marked longitudinal crest. It is believed that they were in cream colour when they are juvenile, and will become blue or purple when they grow up.
References: 1. Felix Wang
Special Thanks to Felix Wang and Tony Coenobita