Alex Hyde / Cleg fly / Horsefly (Haematopota pluvialis) sucking blood from human.

Nick Upton / Cleg fly / Horsefly (Haematopa pluvialis) sucking blood from photographer's arm, Wiltshire pastureland, UK, June.

Nick Upton / Stable fly (Stomoxys calcitrans) piercing skin to suck blood from photographer's ankle, Samos, Greece, August.

David Maitland / Pigeon louse fly (Ornithomya avicularia) amongst the feathers of a Tawny Owl (Strix aluco). Feltwell, Norfolk, UK.

Nick Upton / Sequence 2 / 4. Cleg fly / Horsefly (Haematopa pluvialis) sucking blood from photographer's hand Wiltshire pastureland, UK, June.

Nick Upton / Sequence 1 / 4. Cleg fly / Horsefly (Haematopa pluvialis) about to pierce human skin a second time with blade like mouthparts. Wiltshire pastureland, UK, June.

Nick Upton / Sequence 3 / 4. Cleg fly / Horsefly (Haematopa pluvialis) excreting excess water as it swells up with blood sucked from photographer's arm, Wiltshire pastureland, UK, June.

Nick Upton / Sequence 4 / 4. Cleg fly / Horsefly (Haematopa pluvialis) swollen with blood sucked from photographer's hand, Wiltshire pastureland, UK, June.

Premaphotos / Horse fly (Philopomyia sp) showing multifacetted compound eyes and thick, biting proboscis, Corfu, Greece

Gary Smith / Cleg fly {Haematopota pluvialis} on human skin with drop of blood, UK