Safety and first aid

March flies

What are March flies?

March flies are stout-bodied flies, 6mm to 25mm in length with very large eyes. There are more than 200 species in Australia and they are sometimes known as horse flies or tabanids.

The females of most species of March fly take a blood meal after inflicting a painful bite with their piercing mouthparts. They can be annoyingly persistent when attempting to bite. The adults of both sexes feed on nectar and plant juices.

March flies can be a serious pest to:

  • humans
  • livestock
  • domestic animals
  • wildlife.

Where do March flies breed?

March flies breed in places such as:

  • damp soil
  • rotting vegetation
  • sand
  • rot holes in trees.

Their lifecycle from egg to adult can take months or years depending on the species and soil temperature.

Adults generally live for 3 to 4 weeks.

Where are March flies found in WA?

March flies can be found anywhere in Western Australia but are more common in warmer climates. 

March flies respond to particular environmental conditions, and often breed in large numbers after heavy rainfall during summer months.

When are March flies most active?

Adult March flies are most active in daylight during the warmer months, particularly on calm, sunny days.

In the tropics, they may continue to be active through the drier winter months.

What are the health impacts of March flies?

March flies are not known to transmit diseases to humans or livestock in Australia.

Their bite, however, can cause serious allergic reactions in some people which may require hospitalisation.

Livestock can suffer severe blood loss from repeated biting.

One species of March fly found in the Pilbara and Kimberley regions of Western Australia appears to produce serious symptoms in some people, including:

  • hives
  • fever
  • wheezing
  • in severe cases, anaphylaxis (severe allergic reactions).

What medical treatments are available?

Applying an ice pack or using a mild antihistamine may offer relief from painful bites.

Scratching the bites can result in an infection that may require the application of antiseptic cream or the use of antibiotics.

Patients with a severe allergic reaction should seek urgent medical assistance and advice.

Can march flies be controlled?

It is generally not possible to control march flies using large scale pesticide applications.

This is due to the extensive size of their breeding areas and their ability to travel long distances.

How can I avoid being bitten?

Cover up and use repellents

  • March flies are known to be attracted to dark blue, so it is advisable to avoid wearing blue and other dark colours. Light-coloured, loose fitting clothing will provide some protection when March flies are present.
  • Insect repellents are an important way of protecting yourself against March flies. When outdoors, use an effective insect repellent if March flies are active.
  • Insect repellents containing DEET or picaridin are the most effective. As a general rule, the greater the percentage of DEET or picaridin, the longer the product will remain effective.
    • Always follow instructions on the label.
    • Choose a repellent with an appropriate concentration of DEET or picaridin to match the length of time you are outdoors.
    • Apply directly to skin (except face) and spread evenly with hands.
    • For face application, apply first to hands and then spread evenly on face, avoiding mouth and eyes.
    • Repellents will not be as effective if applied sparingly to the skin.
  • Repellents for children:
    • Under 12 months – repellents containing DEET or picaridin are not recommended.
    • From 12 months – repellents containing up to 10% DEET or picaridin can be used.
    • Application guidelines for children:
      • Do not allow children to apply repellent.
      • Apply repellent firstly to the hands of the carer and then spread evenly to exposed skin of child.
      • Avoid applying repellents to hands, near the eyes or mouth.
      • Do not apply repellent under clothing.
  • Reapply repellent according to the label.
  • The best protection for babies and young children is protective clothing and other forms of insect screening.

Houses and workplaces

  • Fly traps may be useful for reducing populations in areas such as schools and workplaces. Dark coloured boards (for example, 60 cm2), coated with a permanently sticky adhesive have been used with some success overseas. Other commercially available traps may be sourced through the internet.
  • Screen all doors and windows.

Travelling and camping

  • Screen caravans and tents.
  • Utilise screened shelters and avoid areas where March flies are active.

More information

Remember

  • March flies are annoyingly persistent when attempting to bite.
  • Their bites can be very painful.
  • March flies can be found anywhere in Western Australia but are more common in warmer climates.
  • Patients with a severe allergic reaction should seek urgent medical assistance and advice.

Acknowledgements

Public Health


This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

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