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:

• severe localised swelling
• intense itching
• 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.

Severe, painful swelling may require further medical assistance and use of steroidal anti-inflammatory medications and/or other treatment options.

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.

Reporting March fly reactions

If you have experienced a severe allergic reaction to a March fly bite, please complete the follow-up questionnaire (external site) and send any March fly samples (external site) to the Department of Health, if you are able to collect them.

The information and specimens you provide will help to improve our understanding of the most common regions and times of year that are high risk for March flies, and which species are most likely associated with severe reactions.

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

• Wear long, light-coloured, loose fitting clothing.
• Avoid wearing blue and other dark coloured clothing, as they are known to attract March flies.
• Avoid tight fitting clothing, as March flies can bite through them.
• Where possible, avoid exposing your baby or child to March flies. Consider staying indoors, using pram netting or dressing them in loose, long-sleeved clothing, including socks and shoes.

Repel

• Apply an effective insect repellent, containing diethyltoluamide (DEET), picaridin or Oil of Lemon Eucaluyptus (OLE, also known as PMD), evenly to all areas of exposed skin.
• Read the Insect repellent guidelines for more detailed information on which repellents are effective and how to apply them correctly to adults and children.

Houses and workplaces

• Ensure insect screens are installed and in good condition.
• Swat or use insecticide spray if March flies are present indoors.
• 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.

Travelling and camping

• Ensure insect screens are installed and in good condition on tents and caravans.
• Utilise screened shelters and avoid areas where March flies are active.
• Cover up and use an effective insect repellent.

More information

Contact Environmental Health Services at your local government (external site).

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.

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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.