Nuisance of non-biting midges (Chironomidae) for aquarists and for people in the natural environment

There is a group of non-biting midges (Chironomidae, Diptera), which due to the eutrophication of inland waters in urban and suburban areas have become very numerous. Some species of Chironomidae belong to oxygen deficit tolerant organisms, owing to a high content of haemoglobin in their larvae (bloodworms). Due to their high abundance in all types of fresh water bodies (they are the basic food component of invertebrates and vertebrates), freeze-dried and ground larvae of chironomid midges have become a source of fish food used by aquarists. It soon turned out that the ground haemoglobin, whose granules are smaller than 10 mu m in diameter, may cause allergy in both aquarists and in people engaged in production of fish-food (occupational allergy). A high density of chironomid larvae in eutrophicated waters terminates in mass midge emergence; the males form then swarms over reservoirs and adjoining terrains. Particularly well-known is their nuisance in Florida, Japan, and Venice. Mainly in these areas, worries over the adults of these non-biting insects being possible sources of biologically active factors causing allergy have appeared (environmental allergy). Certain allergists claim that such source cannot be haemoglobin, because the enzymatic degradation of this protein during the metamorphosis takes place, but this causes mostly insect body fragments flying in air, such as squams, and setae, etc. In turn, others believe that the degradation is not perfect in all species and their meconium (the first excreta of the emerged adult, "fishy smelling") is the chironomid allergen made available for inhalation.