Many insects that normally dwell on land have colonized the various freshwater habitats that can be found in the tropical rainforest.

Most of these insects must still come to the surface to breathe.

Water beetles and water boatmen hold a bubble of air under their wing covers and periodically come to the surface to replenish it.

Dragonfly nymphs are one of only a few forms of water insects that possess functional gills.

Many aquatic insect species in the tropical rainforest are similar to those in temperate regions.

Male dragonflies are commonly seen flying back and forth along a stretch of water, defending it from other males while waiting for a passing female.

They capture small flying insects with their strong, forwardly directed legs and eat them on the wing.

Their aquatic nymphs eat insects as well as small frogs, tadpoles and fish.

Diving beetles are the largest of the water-dwelling beetles.

Both adults and larvae attack a number of small aquatic animals.

Diving beetle larvae have large, hollow, curved jaws through which they inject enzymes into a prey. These enzymes digest the prey's tissues and convert them into a "soup", which the larvae suck back up through their mandibles.

The giant water bug can be found in slowly moving water.

A voracious carnivore, it stalks its prey through underwater vegetation.

When close to its victims, it strikes quickly and seizes its prey with its forelegs. It has typical piercing bug mouthparts and use enzymes to digest the body contents of it prey.

Giant water bugs, though heavy and noisy, are strong fliers. They are often attracted to lights at night, and tend to fly around the time of a full moon. These flights are frequently a prelude to egg laying.

Giant water bugs are food for large predators, especially crocodiles. Fish do not eat them very often.

Cannibalism has been recorded among these insects, mainly when food supplies are low.

Black Flies and River Blindness

The black fly, an aquatic insect, often bites human beings.

African black flies bite during the daytime, rasping a small wound and sucking up the blood that oozes out.

They can transmit onchocerciasis, also known as river blindness, a serious human disease caused by the nematode worm Onchocerca volvulus.

The larvae of this worm, called microfilariae, are found in the surface layers of a human host's skin and are picked up by a black fly feeding on the host.

The infective larvae that develop from them are deposited in another host when the fly next bites.

The developing worms creep through the subcutaneous layers of the person's body and eventually congregate with other worms in one spot where they become surrounded by fibrous tissue forming a visible nodule.

If the nodules are in the head, the microfilariae tend to invade the eyes, causing blindness.