Hermit crab wood and stone are used by some species). The tip of the hermit crab's abdomen is adapted to clasp strongly onto the columella of the snail shell. Most hermit crabs are nocturnal. Hermit crabs can be divided into two groups: As hermit crabs grow, they require larger shells. Since suitable intact gastropod shells are sometimes a limited resource, vigorous competition often occurs among hermit crabs for shells. The availability of empty shells at any given place depends on the relative abundance of gastropods and hermit crabs, matched for size. An equally important issue is the population of organisms that prey
Nephilengys upon by the spider-eating jumping spider "Portia". At least some species shake their bodies vigorously when touched. Nephilengys Nephilengys is a genus of tropical spiders of the family Araneidae, consisting of two currently described species. (The genus was formerly placed in the Nephilidae and Tetragnathidae.) The genus "Nephilingis" has been split off from this genus. Both genera have been called hermit spiders from the habit staying in their retreats during the day; the name eunuch spiders has been used for "Nephilengys" alone. Males may sever parts of their palpal bulbs after copulation. Females are from 10 mm to 28 mm