There are four stages in the life cycle of chironomid midges. Eggs are laid on the surface of the water. Each gelatinous egg mass may contain up to 3,000 eggs depending on the species. Eggs sink to the bottom and hatch in several days to one week. After leaving the egg mass, larvae burrow into the mud or construct small tubes in which they live. Larvae enlarge their tubes as they grow. Suspended organic matter in the water and in the mud is used as food by the developing larvae. After they grow, the larvae take on a pink color and gradually turn a dark red. Consequently, mature larvae are commonly called “blood worms”. The red color results from an iron containing compound, haemoglobin, that is in the midge’s blood. The haemoglobin allows the larvae to respire under low dissolved oxygen conditions in the bottom mud. The larval stage can take from less that 2 to 7 weeks depending on water temperature. Larvae transform into pupae while still in their tubes. After 3 days, pupae actively swim to the sur-face, and adults emerge several hours later. Adults mate in swarms soon after emerging. Because they do not feed, adults live for only 3 to 5 days.
During summer, the entire life cycle from egg to adult can be completed in 2 to 3 weeks. In the fall, larvae do not pupate, but they suspend development and pass through the winter months as mature larvae. Pupation and emergence of adults occurs the following spring in late March or early April. Several more generations of midges will be produced throughout summer, resulting in mass emergences of adults. In each generation, adults will typically emerge in large numbers for several weeks.
Credits:
BIOLOGY AND CONTROL OF NON-BITING AQUATIC MIDGES
By: Charles Apperson, Michael Waldvogel and Stephen Bambara, Extension Entomology
Follow this link for a pretty decent article on midging.
