Coloured scanning electron micrograph (SEM) of Black fly pupa (Simulium hippovorum). Pupae are encased in a silk cocoon attached to vegetation or other objects in the water. This species has boot-shaped cocoon, with a raised collar in the front. Note the tentacle-like structures, called pupal gills, coming from the anterior region of pupa. These gills are the respiratory organs for the pupa. Loops of silk often surround the gills and may help create miniature eddies around the gills to aid respiration. S. hippovorum has a pair of gills with eight filaments each. They are designed to extract oxygen both in and out of the water. This helps the pupae survive if water levels fluctuate and the pupa is left above the water line. Simulium hippovorumis a blood-sucking insect closely related to mosquitoes. Black flies can transmit filarial worms to humans resulting in a disease called onchocerciasis, which cause blindness. Magnification: x4.
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