I was examining some rain water in a plastic container that flowed from my roof top. At the bottom of the container were rod-like accumulations of blackish dirt (above). Draining most of the water, I collected the blackish remains into a small plastic container used to contain food. By then the black dirt was floating about, taking no definite shapes.
Once the water settled, the rod shapes re-appeared on the bottom of the container. Fascinated, I shook the container to break up the “rods” and left a video-cam on to record what causes the reappearance of the rods (see video below).
A number of longish, reddish worm-like wrigglers (actually larvae) were seen in the water re-assembling the blackish dirt into tubes (below). At the end of one of the larvae can be seen short, branched tentacle-like structures. These are the pro-legs. Apparently, the larvae reside inside the tubes.
Trawling the internet provided me with answers. These wrigglers are the larvae of midges, also known as Chironomids (Chironomus sp.). Some of these small, non-biting flies (Diptera: Chironomidae) may look like mosquitoes. They sometimes form large swarms or clouds near water bodies LINK.
The immature stages of the life cycle develop in water. The eggs are in gelatinous packages that float in the water, attached to water plants or sink to the bottom LINK. The reddish wrigglers are the larvae, the colour is due to the presence of hemoglobin that allows them to survive in low oxygen water. These larvae construct tiny tubes through which they draw stream of water to feed on the microscopic organisms. Inside the tubes the larvae pupate. The adult midge is a small fly-like insect. Other common names include Drain Flies and :are Flies.
Unfortunately I was not able to photograph the adults. Besides being tiny, the flies immediately flew off when the lid of the container was opened.
7th December 2017