March flies

March flies, also known as horse-flies or tabanids, are classified into the Order Diptera (two-winged flies) and the Family group known as Tabanidae. In Australia, there are more than 200 different March fly species.

March flies can be a serious pest to humans, livestock, domestic animals and wildlife, and are annoyingly persistent and painful when attempting to bite. Whilst March flies are not known to transmit diseases to humans or livestock in Australia, their bite can cause serious allergic reactions in some people which may require hospitalisation. Livestock can suffer severe blood loss from repeated biting.

Biology and ecology

Distribution

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

Activity

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.

Breeding

March flies breed in places such as damp soil, rotting vegetation, sand and 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 three to four weeks.

Feeding

As with most biting flies and mosquitoes, it is only the female that requires a bloodmeal to source protein to lay eggs. They have strong, piercing mouthparts to extract blood from their host. The males feed on plant nectar only.
The maggot larvae are quite aggressive predators too, preying on the larvae of other insects. March fly larvae can bite if handled.

Health impacts

March flies can be a serious pest to humans, livestock, domestic animals and wildlife, and are annoyingly persistent and painful when attempting to bite. Whilst March flies are not known to transmit diseases to humans or livestock in Australia, their bite can cause serious allergic reactions in some people which may require hospitalisation. Livestock can suffer severe blood loss from repeated biting.

One tabanid species found in the Pilbara, Kimberley and northern Goldfields regions of Western Australia appears to produce serious symptoms in some people, including hives, fever, wheezing, and in severe cases, anaphylaxis (severe allergic reactions). Research is currently underway to characterise proteins in the saliva of this species that may be responsible for severe allergic reactions and to determine whether similar proteins are present in the saliva of other tabanid species.

Treatment

Symptomatic treatment, including application of an ice pack and use of an antihistamine, may offer relief from painful bites. Scratching the bites can result in a secondary bacterial 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.

Prevention

The simplest way to prevent being bitten by a March fly is to cover up with appropriate clothing and/or apply an effective repellent product.

The following information may further assist in reducing March fly bites:

  • March flies are known to be attracted to dark blue, so it is advisable to avoid wearing blue and other dark colours. Long, light-coloured, loose fitting clothing, including head nets, is likely to provide the most effective protection for humans when March flies are present.
  • Insect repellents are another important means of protecting yourself against March flies, but will vary in their effectiveness depending on the species of March fly.
  • When outdoors, use an insect repellent containing either diethyltoluamide (DEET) or picaridin if March flies are active. 
  • Lotion or gel repellents are the most effective. Always read the label. Apply and re-apply repellents in accordance with the manufacturer’s instructions.
  • Repellent reapplication may be required after swimming, as the product may wash off.
  • Natural or organic repellents are generally not as effective as DEET or picaridin and may need to be applied more frequently.
  • The best protection for babies and young children is to dress them in protective clothing, socks and shoes, and use other forms of insect screening. 
  • Repellent application is not recommended in children under the age of 12 months of age. Repellents containing up to 10% DEET or picaridin can be used on children from 12 months. 
  • Correct application of insect repellent (Healthy WA) is critical in ensuring the product remains effective.
  • People with a history of severe allergic reactions to March fly bites should avoid travel to or work in locations and at times of the year when they have previously experienced such allergic reactions.
Control

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 ability to travel long distances. Similarly, water or land management over such extensive areas of natural habitat is generally not feasible or effective.

In areas where population densities of adult flies are high, protective clothing is likely to be the most effective protection for people.

Adult March flies are often attracted to dark colours and solid shapes, so sticky traps, box traps and other trap types using this attribute may be useful in reducing numbers in localised situations such as in small communities or campsites. However, these methods have not been widely evaluated for Western Australian March fly species.


More information

Medical Entomology
Phone: (08) 9285 5500
medical.entomology@health.wa.gov.au

Last reviewed: 06-02-2020