Midges comprise many kinds of very small two-winged flies. There are 800 species of this family.
- Size is 1.5-5mm. Thorax humped over the abdomen.
- Wings are prominent and head over the abdomen like a pair of close scissors at rest.
- Colour of abdomen is grey or brownish black.
- Legs are small and antenna is prominent. Antenna in male is feathery and called as plumose. Antenna in female is like small hair and is called as pilos.
- Mouth part hanged vertically and adapted for piercing.
- Labrum of mouthpart is sharp.
- Paired maxilla and mandibles are present.
- Hypopharynx carries salivary duct and deliver anticoagulant to the host tissue.
- All the elements do not enter the skin during feeding because mouthpart is only adapted for piercing.
- After complete blood meal, gravid female lay eggs on decaying organic matter.
- Eggs are dark coloured or brown coloured.
- Eggs shape is either cylindrical or banana shaped.
- Size of egg is 0.5mm.
- Egg hatch and larvae develop. Hatching is temperature dependent and takes place in 2-9 days.
- There are 4 larval instars(stages).
- Fully developed larvae is brownish in colour. It has small black head, segmented body and terminal anal gills which enable the larva to move in water.
- Development of larva takes place in 14-25 days depending upon the environmental temperature.
- From the larva, pupa develop. Pupa is black or brownish in colour. Size of pupa is 2-4mm. it is very less active as compared to larva. Cephalothorax can be seen.
- .Respiration takes place through respiratory trumpts.
- From pupa, adult emerges in 3-10 days depending upon the conditions.
- Adult has short life span. Adult move 200m, fertilized, lay eggs and then dies. Only female sucks blood.
- Cause viral diseases like blue tongue and African horse sickness.
- Parasitic infections include Dipetelonema(filarial worm) and onchocerca.
- Cause sweet itch/Queenlands itch in horses. Immediate hypersensitivity reactions occur.
- Destruction of breeding places is very important.
- Use of insecticides is necessary.
- Confinement is neccary
- Where flies are in abundance, human and animals activity should be restricted especially during morning and afternoon b/c during these periods, flies activity is max.
For sweet itch, antihistaminic drugs should be recommended along with the insecticides. Antihistaminic drugs include Meprasan, Anthison, Avil, Incidal.