Hydrotaea irritans

Also known as:

Sheep headfly

H.irritans female

H.irritans male

Scientific Classification

Phylum	Arthropoda
Class	Insecta
Order	Diptera
Family	Trichodectidae

Hosts

Cattle, sheep, and horses.

Identification

H. irritans is morphologically very similar in appearance to Musca. The adult flies are 4-7mm in length, have a green thorax and a yellow abdomen.

Life Cycle

The female lays eggs in the faeces, or decaying vegetation. Eggs then hatch into larvae in the autumn, and begin to mature. However, development is haltered until the following spring. They then undergo pupation, and maturation is complete. Adults emerge in summer.

Pathogenesis

• Cattle
  • Evidence suggests that they transmit summer mastitis

• Sheep
  • Cause extreme irritation
    • Mouthparts rasp the skin to feed on secretions and exudate
  • Leads to self-inflicted damage
    • E.g. 'Broken Head'
  • Secondary bacterial infection may occur
  • Blowfly strike may follow