Natural History of Midges

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Kingdom: Animalia
Phylum : Arthropoda
Subphylum: Hexapoda
Class: Insecta
Order: Diptera
Infra-order: Culcimorpha
Family: Chironomeidae
“Midge” from Old English “mycg” meaning “small fly”                                     Ref. Wikipedia

In Family Diptera, identification can often only be by terrestrial adult, and not possible to identify as aquatic larvae. Chironomidae are by far the largest family of aquatic insects. The larvae are recognizable because they have anterior and posterior pairs of prologs.  They inhabit all types of permanent and temporary aquatic habitats. The short lived adults cause human allergies. Feeding habits of different species of midges vary widely, herbivore-detritovore as well as carnivores.  Many larvae are free living, but most species construct loose cases of substrate cemented together with salivary secretions. Most larval midge herbivores and detritivores graze on fine particles on the substratum, but some are filter feeders that construct webs to filter water that they circulate through their case (sometimes called their retreat). 
 Ref. W.L.Hilsenhoff in Ecology and Classification of North American Freshwater Invertebrates, 1991


http://bugguide.net/node/view/55560  Green Midge on dandelion bloom
True midges, Diptera: Chironomidae are benthic for the majority of their larval lives.  They swim within the water column during the earliest stages of larval life. [As with bacteria and fungi, a planktonic stage precedes a sessile or benthic stage.]
Ref. J.H.Thorp & A.P.Crouch in Ecology and Classification of North American Freshwater Invertebrates

Larval midges have a hard head capsule, one pair of fleshy pro-legs right behind the head, and another pair at the tail end. No spiracles. One type of midge has a symbiosis with a type of colonial alga that provides food and shelter for the midge larvae, in trade for the algae gaining advantages in reproduction, dispersal and substrate placement.
Ref. S.A.Marshall  Insects-Their Natural History and Diversity, 2006


Larval Midge















Midges in cases on rock in stream bed

Orthocladinae (Diptera:Chironomidae) consume protozoa as a large portion of their diet.
Ref. W.D.Taylor 1980 Transactions of the American Microscopal Society 99:260-368
Larval water mites parasitize 20-50%  of mature Chironomidae larvae.  Experiments have shown that these larval water mites impair the midges vitality, growth, mobility and fecundity.
Ref.B.P.Smith 1983 pp 79-85   in Biological Control of Pests by Mites
Mermithids parasitize Crictopus midges that live inside Nostac algal ponds.
Ref. G.O.Poinar Jr. in Ecology & Classification of North American Freshwater Invertebrates, 1991
Swimming Pupae of Tanypodine Chirironomidae are parasitized just below the surface film of water. They construct cases for defense, but are also themselves predators on other invertebrates including other Chironomidae.
Ref. I.M.Smith & D.R.Cook in Ecology & Classification of North American Freshwater Invertebrates, 1991
Most species of midge are quite tolerant of lowered oxygen levels. Some can survive where O2 levels are non-detectable. These species are usually red and contain a type of hemoglobin that retains oxygen. These so-called “blood worms” operate in sewage lagoons and organically polluted areas of lakes and streams. After completing development, the pupa swims to the surface where emergence occurs. Adults do not feed and live < 2 weeks.
Ref.L.C.V.Pinder 186 Annual Review of Entomology 31:1-23
“Bloodworms” are often in polluted water or anoxic mud. They feed by netting microorganisms that are feeding on the organic matter around them. Some midges feed on dead leaves, some on living vegetation. Some are predators, some parasites on stone flies, mayflies and caddisflies. Metriocnemus knabi are found in the debris at the bottom of pitches plants.


Blood Midge
The majority of the insect attracted to porch lights in North America are 2000 or so species of chironomid midges. No scales, no biting mouth parts. They number as many as tens of thousands per square meter soil surface as terrestrial adults. They are very important in both terrestrial and aquatic food chains. They are abundant in every body of water on earth except the open ocean.  Numerous on the sea-shore. Some male midges have flightless wings that propel them across the sea surface. Their females totally lack wings and legs, resembling larvae.
Abundant at cool temperatures, midges are the most common insect during winter months in North America. They have been recorded out at temps as low as -16ᵒC.The winter-active Diamesa species walks on the snow near running waters, on mild days in March. Some midges are adapted to high temperatures. One species can dry up in its larval stage, then resume activity when wetted.
 Ref. S.A. Marshall, as previously cited


Written by Geof Gaiser

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