. ▁ ▁Description ▁ ▁These ▁c rab s ▁are ▁relatively ▁large , ▁with ▁a ▁car ap ace ▁bread th ▁of ▁up ▁to ▁. ▁Depending ▁on ▁the ▁species , ▁the ▁car ap ace ▁may ▁be ▁v ivid ly ▁col oured , ▁especially ▁in ▁males ▁of ▁N . ▁h ong k ong ense ▁( or ange ▁to ▁red ), ▁N . ▁ac ul atum ▁( dark ▁blue ) ▁and ▁N . ▁z hu ha ien se ▁( light ▁blue ). ▁Ch el ip eds ▁are ▁usually ▁une qual , ▁more ▁so ▁in ▁larger ▁males , ▁where ▁one ▁ch el ip ed ▁is ▁relatively ▁much ▁larger ▁than ▁the ▁other . ▁This ▁may ▁be ▁of ▁use ▁in ▁territorial ▁f ights , ▁as ▁the ▁c rab s ▁are ▁very ▁ag gress ive ▁towards ▁cons pec ific s . ▁ ▁Distribution ▁and ▁habitat ▁ ▁C rab s ▁of ▁the ▁genus ▁Nan ha ip ot am on ▁inhab it ▁the ▁banks ▁of ▁small ▁to ▁medium - s ized ▁hill ▁streams , ▁p addy ▁fields ▁and ▁sw amps . ▁Although ▁not ▁particularly ▁a ▁low land ▁species , ▁they ▁usually ▁do ▁not ▁occur ▁above ▁approximately ▁ 5 0 0 ▁meters ▁above ▁sea ▁level . ▁Most ▁species ▁are ▁no ct urn al , ▁leaving ▁their ▁bur rows ▁at ▁night ▁to ▁for age . ▁Species ▁belonging ▁to ▁this ▁genus ▁have ▁been ▁recorded ▁from ▁Hong ▁Kong , ▁Mac au , ▁Gu ang d ong , ▁F uj ian , ▁Z he ji ang , ▁Taiwan ▁and ▁D ong y in ▁Island . ▁ ▁Conserv ation