Haematobia irritans

The hornfly Haematobia irritans occurs in association with cattle around the world, including in Canada.


The hornfly Haematobia irritans occurs in association with cattle around the world, including in Canada.  The adult flies tend to spend most of the time on the host and both females and males blood-feed repeatedly, especially when it is hot and humid.  The females lay eggs in fresh cattle faeces and in ideal temperature and moisture conditions the entire life cycle can be completed in a couple of weeks.  Overwintering is primarily as pupae beneath faecal masses.


Phylum: Arthropoda
Subphylum: Uniramia
Class: Hexapoda
Order: Diptera
Suborder: Cyclorhapha
Family: Muscidae

As well as the horn fly, the Family Muscidae includes the house fly (Musca domestica), the face fly (M. autumnalis) and the stable fly (Stomoxys calcitrans). Male and female horn flies and stable flies blood feed on their hosts.

Note: Our understanding of the taxonomy of helminth, arthropod, and particularly protozoan parasites is constantly evolving. The taxonomy described in wcvmlearnaboutparasites is based on that in the seventh edition of Foundations of Parasitology by Larry S Roberts and John Janovy Jr., McGraw Hill Higher Education, Boston, 2005.


Adult Haematobia irritans are small, dark flies measuring up to approximately 4 mm in length. The thorax has two dorsal longitudinal dark stripes.

Host range and geographic distribution

Cattle are the primary hosts for horn flies, but they may be also be found causing problems on horses. Haematobia irritans is found in Europe, North and Central America, including Canada, and Australia.

Life cycle - direct

Adult male and female H. irritans are almost obligate parasites of cattle and spend most of their time on the hosts. They tend to congregate along the back and withers and around the head. The adult females mate only once, in the hair coat, and then leave the host for short periods to lay eggs in freshly passed cattle feces on the ground. Under ideal conditions the eggs hatch in a day. There are three larval stages lasting approximately a week and the larva then produces a cocoon and pupates. After approximately one further week, the adult fly emerges from the pupa and quickly finds a new host. Thus there can be several generations of horn flies in a summer.


The life cycle of horn flies matches very well with that of their hosts and they are very successful on cattle in western Canada and in other parts of the world. Horn flies over winter as pupae in feces.

Pathology and clinical signs

Individual cattle can harbour many thousands of horn flies. These feed many times each day by repeatedly inserting and withdrawing their proboscis, aided by the adjacent mouthparts which help drive the proboscis deeper. These activities, coupled with large burdens of flies, can cause considerable irritation, which can adversely affect productivity. The wounds caused by the horn flies may also attract other flies that worsen the situation. Haematobia irritans is the intermediate host for Stephanofilaria stilesi, a cutaneous nematode that affects the ventral abdomen of cattle.

Treatment and control

A large number of topical products, including ear tags, as well as the topical (pour-on) preparations of the endectocides, are approved in Canada for treatment and control of horn flies on cattle.  Some cannot be used in lactating dairy cattle.  These products, properly applied, can be quite effective because the flies spend almost all their lives on the hosts. A major problem in Canada, however, is the widespread resistance of the flies to the synthetic pyrethroids used for control.  In Canada, the use of the non-endectocide products is controlled by the Pest Control Products (PCP) Act.

Several avermectin products (most applied topically - pour-ons) are approved for horn fly control in Canada.

 Drug(s)  Product(s)
Cypermethrin and Diazinon ELIMINATOR EAR TAGS
Dichlorvos with Pyrethrins DISVAP III
Eprinomectin  EPRINEX POUR-ON
Lambda-cyhalothrin SABER EAR TAGS AND POUR-ON
Malathion VARIOUS
Permethrin VARIOUS
Pyrethrins in combination DISVAP IV
Rotenone and Sulphur DRI_KIL LOUSE POWDER

Additional information on the product mentioned is available from the Compendium of Veterinary Products (Twelfth Edition, 2011), or from the manufacturers.

Public health significance

Although horn flies will sometimes cause annoyance to people, especially those working with affected cattle, other than horses they feed on other hosts only very rarely.


Cortinas R et al. (2006) Ectoparasites of cattle and small ruminants. Veterinary Clinics of North America Food Animal Practice 22: 673-693.
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