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Which Flies are Biting Cattle? 

Their Defensive Behaviors Will Tell You.

Cattle are not passive hosts to the various flies pestering them. They do fight back. Defensive behaviors are reactions to specific flies in the pasture. Each fly species has a preferred landing site. Producers can tell what kinds of flies are attacking cattle by the animals’ reactions and the distribution of flies over their bodies. Responses depend on the annoyance and the pain inflicted by the pest.

 

Stable flies

  • Blood feeders that prefer to bite the legs and bellies of cattle.
  • Possess a large bloodsucking proboscis (mouthpart); they feed once or twice a day and inflict a bite many times more painful than that of a mosquito. 
  • Economic threshold: 10-12 flies per animal.
  • Cattle reaction: foot stomping, tail switching, bunching, and spending lengths of time in water for protection from fly.
  • Control: Stable flies remain on hosts long enough to feed. But because of this fly’s painful bite, feeding is often interrupted by the animals’ defensive reactions. Therefore each fly has to visit the same or different hosts several times to obtain a full blood meal. This shorter time stable flies spend on their hosts makes their control difficult.

Horn Flies

  • Blood feeders found on backs of cattle. As temperatures rise, horn flies move down the sides of cattle.
  • Horn fly mouthparts are developed for blood sucking, but are smaller than those of stable flies. Each female horn fly feeds up to 40 times a day, biting at least that many times.
  • Economic threshold: 200 flies per animal or 100 per side.
  • Cattle reaction: switching tails over backs (rump), throwing heads over shoulders, and bunching. 
  • Control: Horn flies spend all of their time on their hosts, leaving for short periods of time to lay eggs on fecal pats just deposited by their hosts. This closer association with their host makes horn flies easier to control with insecticide applications.
  • When disturbed into flight, horn flies land on the same or neighboring cattle with many flies exchanged among them. Consequently, not all members of the herd need to be treated with insecticides because every fly eventually lands on a treated host and is killed.

Which are biting – horn flies or stable flies?

Bunching caused by stable flies differs from that caused by horn flies. Cattle bunched by horn flies throw their heads over their backs, while cattle bunched by stable flies do a lot of foot stomping. In addition, stable fly attacks most often result in cattle bunching at corners of pastures, a behavior seldom seen in cattle attacked by horn flies. 

Face flies

  • Non-blood-sucking feeders. Because of sponging mouthparts, they can only feed on serum/blood secretions from pre-existing wounds.
  • Face flies are indistinguishable from house flies. But after landing on a host’s face, face flies move immediately to the eyes. Their mouthparts have sharp teeth used for scraping conjunctival tissues. This irritation increases tear production and weeping on the cheeks of cattle.
  • Economic threshold: 10 flies per animal.
  • Cattle reaction: flapping ears and shaking heads from side to side. 
  • Control: Face flies visit their hosts one to two times a day for short periods of time. This behavior and the sensitive body areas visited make insecticidal control difficult.

House flies

  • Non-blood-sucking feeders. Because of sponging mouthparts, they can only feed on serum/blood secretions from pre-existing wounds.
  • Face flies are indistinguishable from house flies. But after landing on a host’s face, houseflies move to the nostrils and mouth.
  • Cattle reaction/Control: Houseflies do not harm cattle and cause little defensive behavior.

Source: Dr. Alberto B. Broce, emeritus professor, Kansas State University Department of Entomology, and Kansas Veterinary Quarterly, published by Kansas State Research and Extension.