This year I have been carrying out a survey of the invertebrates of the saline lagoons at Rye Harbour and am currently in the process of identifying the samples collected during the summer. A good proportion of the specimens are chironomids (non-biting midges or gnats), a large and diverse group of flies usually associated with wetland habitats.
Often mistaken for mosquitoes, these midges don’t feed on blood (hence the sobriquet ‘non-biting’, though perhaps 'non-sucking' would be more accurate) and have jaws rather than piercing mouthparts. Adults usually feed on nectar, pollen or honeydew, while the largely aquatic larvae ingest a wide range of foods including algae, wood debris and even on occasion other invertebrates (including other chironomids). Some, such as members of the genus Cricotopus (above), feed within the leaves of aquatic plants and yet others are parasitic on other aquatic animals such as mayflies, sponges and even fish. In common with many other flies, chironomids often form huge mating swarms, sometimes numbering in the hundreds of thousands or even millions. These swarms are initially made of males, and attract females from the surrounding area which fly into the swarm to mate. Males are attracted to females within the swarm by homing in on the frequency of their wingbeats, which they achieve through specialised receptors on their feathery antennae (clearly visible in the above image). In some cases these swarms can cause a serious nuisance, damaging surfaces with their droppings, making driving difficult or dangerous, and even provoking an allergic reaction in sensitive people (apparently around 20% of the population are susceptible).
Image: Barry Yates
Non-biting midges, both larvae and adult, are eaten by a wide range of animals, which as well as predatory invertebrates includes fish, amphibians, bats and birds. For familiar species such as Dunlin and Sanderling, these tiny flies form an important part of their diet, while Swallows and martins hunting over water bodies in spring and late summer will often be feeding largely on chironomids. A closely related group of flies, the ‘glass midges’, are harvested by the local populations in East Africa as food. The bodies of millions of flies are compacted into solid masses known as ‘kungu cakes’ which can be fried like burgers or grated to add flavour to stews. The famous explorer David Livingstone, who described these cakes in an account of his African explorations, considered that they tasted ‘not unlike caviar’!