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

MORPHOLOGY- HORSE FLY

• Large and robust fly

Head

• Eyes: Large compound eyes, unicolorous and horizontally banded. Holoptic in males and dichoptic in females. Ocelli vestigial
• Antenna: 3 segmented and porrect. Third segment is the largest and equal to the 1^st and 2^nd put together. Third segment  has a tooth like projection/spur at the base and 4 annulations
• Mouthparts:  cutting and sponging type. Coarse biting parts, mandibles are blade or sword like, maxillae ending in rasp like structures distally. Mandibles cut the skin of the host while the maxillae probe deeper, hypopharynx adds the anticoagulant and blood is drawn into the food channel
• The flies are pool feeders - Telmophagy
• Labium ends in labella containing the pseudotracheal membrane which also helps to lap up blood during the feeding process. Maxillary palps are two segmented and prominent
• The coarse mouth parts and feeding habit of the tabanids frighten the host and hence the tabanids are interrupted while feeding which necessitates the intermittent feeders to visit many animals for engorgement. This intermittent feeding habit of Tabanids makes them potential vectors of diseases

Thorax

• Has longitudinal white stripes
• Wings are clear with the 4^th radial vein being forked at the apex
• Discal cell is hexogonal in shape

Abdomen

• Brown  in colour
• Frequently has longitudinal stripes