Family Culicoides(Midges)

Midges comprise many kinds of very small two-winged flies. There are 800 species of this family.

Morphology:

• 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.

Life Cycle:

1. After complete blood meal, gravid female lay eggs on decaying organic matter.
2. Eggs are dark coloured or brown coloured.
3. Eggs shape is either cylindrical or banana shaped.
4. Size of egg is 0.5mm.
5. Egg hatch and larvae develop. Hatching is temperature dependent and takes place in 2-9 days.
6. There are 4 larval instars(stages).
7. 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.
8. Development of larva takes place in 14-25 days depending upon the environmental temperature.
9. 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.
10. .Respiration takes place through respiratory trumpts.
11. From pupa, adult emerges in 3-10 days depending upon the conditions.
12. Adult has short life span. Adult move 200m, fertilized, lay eggs and then dies. Only female sucks blood.

Pathogenesis:

• 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.

Control: 

1. Destruction of breeding places is very important.
2. Use of insecticides is necessary.
3. Confinement is neccary
4. 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.

Treatment:

For sweet itch, antihistaminic drugs should be recommended along with the insecticides. Antihistaminic drugs include Meprasan, Anthison, Avil, Incidal.