[1] The head is vertex with no erect scales but has numerous curved hair-like structures known as setae.

[1] The male of this species has long legs that allow it to walk on water and large claws used to grip females during mating.

The larvae are found in rock pools that occur within the spray zone above the high tide of the coast.

The larvae can occur in both permanent and temporary rock pools, and can tolerate a wide range of water salinity levels.

[6][7] Adults of this species use their long proboscis to feed on the blood of birds, humans, and other coastal animals.

[8] Unlike other mosquito species, the female does not require a blood meal to produce their first batch of eggs.

In early spring, adult mosquitos emerge in large numbers from the rock pools.

[9] The larvae of O. fuscus are known to be infected by Coelomomyces opifexi, a parasitic fungus that uses copepods as intermediate hosts.