VPA 221: Veterinary Entomology and Acarology (1+1)

LIFECYCLE - SHEEP NASAL FLIES

• The flies are larviparous
• The female fly darts at the sheep 
• When the sheep raises its head it deposits a larvae around the nostril of the sheep 
• The first stage larvae then crawls into the nasal passage 
• The larvae moves within using its oral hooks and feeds on the excess nasal discharge produced by the affected sheep
• The rate of the development of the first instar varies, may take just 2 weeks or could get extended to many months
• The larvae moults to form the second stage larvae which moves into the frontal and maxillary sinuses, here they develop rapidly and form the third stage mature larvae 
• Generally the third stage larvae is sneezed and the pupation occurs on the ground 
• Usually the larval development is completed in 25 days time but can be extended to 9 months in unfavourable conditions 
• The adult emerges in a month’s time