Fly Biology / Identification
Horseflies or March flies are biting flies from the family Tabanidae.
There are some 200 species of Tabanids in Australia. Tabanids are serious pests of wildlife, horses, cattle and people with outbreaks commonly occurring from mid to late September and continuing through the summer months. (In the tropics, they can continue to be active through the drier winter months too.) They are stout bodied flies, typically between 6 – 25 mm in length, with large eyes. The wings are held in a single plane over the abdomen when at rest. Adult Tabanids live for between 3-4 weeks and are strong robust fliers.
Only the female flies bite their victims. Female horseflies are mainly active during the day. They use their sharp blade like mouth parts to slash and pierce the skin and have been known to cause painful bites and serious blood loss in some animals. They can be annoyingly persistent when attempting to bite. Males have green metallic eyes which meet in the middle of the head. Both sexes commonly feed on nectar and other plant material.
The breeding places include damp soil, rotting vegetation, sand and rot holes in trees, with the larvae feeding on animal and plant material within the substrate. The life cycle can take many months or even years, depending on the species and soil temperatures. After emerging, the adults mate and the females disperse from the breeding site in search of blood meals. They are capable of travelling great distances in search of blood meals.
March flies are not known to transmit disease to humans or livestock, though their bites can cause adverse reactions in some people, occasionally needing hospitalisation. Livestock can suffer severe blood loss from repeated biting.
A few simple measures can be taken to minimise the risk of bites.
- Fly trapping with the EQUITHOR H‑Trap can be very useful for reducing populations in localised areas.
- March flies are known to be attracted to dark colours, so it is advisable to avoid wearing dark clothes.
- Light-coloured, loose-fitting clothing and insect repellents will provide protection when March flies are present.
The allergic reaction occurs in response to the saliva injected by the fly to prevent the blood from clotting. The application of an ice pack or a mild antihistamine may relieve painful bites. Secondary infection due to scratching the bites may require the application of antiseptic cream or systemic antibiotics. People with a severe allergic reaction should seek urgent medical assistance and advice.
Control of these flies using pesticides is generally not possible due to their extensive breeding areas and ability to fly long distances from breeding sites. The most effective repellents for March flies contain diethyl toluamide (DEET) at between 5 and 20 per cent (50-200g/litre) and are most effective in lotion form. As with all chemicals, repellents should be applied in accordance with the manufacturer's instructions, especially to infants and young children.
The stable fly Stomoxys calcitrans is a widespread pest that mainly bites horses, cattle, domestic animals and people.
The stable fly looks very similar to the common housefly and it is often difficult to distinguish them apart.
Adult flies measure 8 mm in length and are grey in colour, they have 4 dark stripes along the top of the thorax and several dark spots on the abdomen. They have long slender mouth parts that extend forward from the head. Both male and female flies are blood sucking.
The buffalo fly Haematobia irritans exigua is also known to be a serious pests of cattle and horses. Adults are small in size, usually between 3.5 – 4 mm, and able to travel up to 10 Km in search of their initial host. They commonly live for 2 - 3 weeks and are able to feed between 10 - 40 times per day. These flies are unable to survive long periods away from their host and are mainly found in the mid to upper regions of Australia.
