TINY Creatures that Absorb Water Vapor from Air

Source - Wikipedia.org

Crabs, lobsters, crayfish and shrimp all share one physical attribute - they all have external skeletons. This skeleton surrounds nearly all their body organs and protects them from predators.
One structure of their body, pleopods, exists outside their skeleton. 


Pleopods of creatures on land

Source - animalcrossing.wikia.com

Source - derelia.com

Land-living brethren of crabs and lobsters, pill bugs, have succeeded in colonizing land by adapting their pleopods to absorb water vapor from air that is not saturated with moisture.
Pill bugs can loose as much as 30% of their body-moisture and still survive by replenishing this loss by absorbing water vapor in unsaturated air.
Their major loss of body-moisture is through evaporation from the body surface. One of the reasons to roll up into a ball is to reduce the body surface susceptible to promoting evaporation.


Other creatures that absorb water vapor

Flea Larvae
Source - en.wikipedia.org

Book lice
Source - asktheexterminator.com

Silverfish
Source - silverfishbugs.net

Other creatures that absorb water vapor from air are flea larvae, book lice, silverfish, meal worms and ticks.










Why are all of nature's creations that can absorb water vapor from the air, so tiny? Is this a dependency on the amount of water vapor in the atmosphere? Is this a dependency on the size of the water vapor absorbing body structure?