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Specialized habitats

(Hemiptera), skate on the water’s surface, so they

are really inhabitants of the air rather than the

ocean, which is beneath their feet.

Although none have colonized the open sea,

numerous families of beetles have adapted to and

specialized for life on the shoreline, for example

huge numbers of Anthicidae, Staphylinidae,

Ptiliidae, and Histeridae can be found in piles of

rotting seaweed cast up above the high-tide mark,

where they feed on fly larvae or decaying organic

matter. These beetles can survive temporary

immersion, and if dropped into seawater usually

climb onto floating debris or skate on the surface

tension and immediately take flight.

Other groups, particularly Carabidae, are

nocturnal hunters; they shelter under beached

flotsam during the day, and patrol along the

strandline at night for sand hoppers and other

crustaceans or marine worms that have ventured

up onto the beach. These include Eurynebria

complanata, a large and striking, pale yellow and

black inhabitant of Atlantic and Mediterranean

SALT WATER

The open sea is one of the last great habitats that

has never been conquered by beetles, although

beaches, sand dunes, and even the strandline

support a rich and varied beetle fauna. Many

beetles live in fresh water, but these are descended

from land-living ancestors, and the larvae of

almost all freshwater beetles have to leave the

water to pupate on land, even those which then

return to the water as adults. Pupation on land is

probably too difficult and unreliable in marine

environments, where the distance to the nearest

dry land may be enormous and unpredictable.

However, since insects in general are almost

absent from the sea, even those insects that do not

have a pupal stage, the pupation site cannot be

the only reason for the lack of truly marine

beetles. There must be other factors that keep

them out. It is likely that, having evolved and

diversified on land, insects lack physiological

adaptations for life in salt water; also most of the

available ecological niches are already occupied

by crustaceans, which were there first. One of

the only truly offshore oceanic insects, not beetles

but true bugs, the ocean strider genus Halobates

above | Cicindis horni (Carabidae) A rare

semiaquatic beetle of the Salinas Grandes

salt pans of Argentina, which enters the salt

water to hunt for fairy shrimps.