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

BLACK FLIES - PUPA

• Obtectate
• Mature larva is a pharate pupa within the larval skin. The pharate pupa spins a cocoon often slipper shaped, brown in colour with the closed end directed upstream and the open end downstream which helps to prevent the cocoon getting torn off from the substrate
• Cocoon is formed within an hour of the last larval skin being shed
• The head and the thorax of the pupa are combined to form cephalothorax
• There is the presence of a segmented abdomen which has spines and hooks on it to engage with the threads of the cocoon and retain the pupa in its place
• The cephalothorax bears a pair of prominent, filamentous, elongate, branched pupal gills which trail downstream of cocoon. These are homologous to the respiratory trumpets
• Pupa does not feed and becomes darker as the adult develops. The mature pupa takes a silvery appearance when a film of air is seen between the pharate adult and the pupal cuticle
• When the pupal exuviae splits, the adult floats up to the surface of water in a bubble of air
• Mass emergence of thousands of adults takes place (communal breeder) resulting in thousands of bubbles on the water surface giving the appearance of  boiling water!!
• Pupal period lasts for 2-6 days
• Newly emerged adults crawl up some immersed objects
• In tropical countries continuous breeding occurs