Chris Mattison / Tiger Leech (Haemadipsa picta). Danum Valley, Sabah, Borneo.

Yukihiro Fukuda / Close up of the mouth and nose of a Japanese giant salamander (Andrias japonicus) with two Leeches (Hirudinea) attached, Japan, March

Niall Benvie / 2020VISION / Leech (Hirundinea), Scotland, UK, March meetyourneighbours.net project

MYN / Piotr Naskrecki / Close up of sucker of North american leech (Macrobdella decora) swimming underwater, Concord, Massachusetts, USA, May. meetyourneighbours.net project

MYN / Piotr Naskrecki / North american leech (Macrobdella decora) Concord, Massachusetts, USA, May. meetyourneighbours.net project

MYN / Piotr Naskrecki / North american leech (Macrobdella decora) underwater, Concord, Massachusetts, USA, May. meetyourneighbours.net project

MYN / Piotr Naskrecki / North american leech (Macrobdella decora) swimming underwater, Concord, Massachusetts, USA, May. meetyourneighbours.net project

Willem Kolvoort / Barbel (Barbus meridionalis petenyi) with leech, Albania, May

Sue Daly / Dover Sole (Solea solea) with Ichthyobdellid leeches. Channel Islands, UK, August.

Sue Daly / Dover Sole (Solea solea) with Ichthyobdellid leeches. Channel Islands, UK, August.

Sue Daly / Dover Sole (Solea solea) with Ichthyobdellid leeches. Channel Islands, UK, August.

Simon Colmer / Leech (Hemiclepsis marginata) on white background, UK

Jouan & Rius / Photographer, Catherine Jouan, removing Leech (Hirudinea) from her foot, Borneo, Sarawak, Malaysia. Model released

Tim Laman / Borneo tiger leech (Haemadipsa picta) feeding on human skin, Gunung Palung National Park, Borneo, West Kalimantan, Indonesia

Tim Laman / Borneo tiger leech (Haemadipsa picta) two individuals appear to be mating on a leaf. Gunung Palung National Park, Borneo, West Kalimantan, Indonesia

Tim Laman / Borneo tiger leech (Haemadipsa picta) two individuals appear to be mating on a leaf. Gunung Palung National Park, Borneo, West Kalimantan, Indonesia

Tim Laman / Pulling off Tiger land leeches (Haemadipsa picta) during a hike in the rainforest, Gunung Palung National Park, Borneo, West Kalimantan, Indonesia

Tim Laman / Pulling off Tiger land leeches (Haemadipsa picta) during a hike in the rainforest, Gunung Palung National Park, Borneo, West Kalimantan, Indonesia

Tim Laman / Borneo Tiger leech (Haemadipsa picta) engorged with blood opn human hand, Gunung Palung National Park, Borneo, West Kalimantan, Indonesia

Tim Laman / Close up of Tiger leech (Haemadipsa picta) on a leaf in tropical rainforest, waiting for passing victim. Borneo

Tim Laman / Close up of Tiger Leech (Haemadipsa picta) on a leaf in tropical rainforest, waiting for passing victim. Borneo

Stephen Dalton / Medicinal leech (Hirudo medicinalis) in water, controlled conditions

Jane Burton / Three spined stickleback {Gasterosteus aculeatus} with freshwater Leech {Pisciola geometra} attached, captive, from Europe

Doug Perrine / Tiger sharks (Galeocerdo cuvier) North Shore, Oahu, Hawaii, USA, Central Pacific Ocean, note: shark at centre has parasitic leech on side of face

PREMAPHOTOS / Leech {Haemadipsa zeylanica} engorged with blood after feeding, in rainforest, Thailand

PREMAPHOTOS / Leech {Haemadipsa zeylanica} in alert pose, waiting for a passing animal to feed from, Thailand

Doug Wechsler / Foot swollen by edema due to allergic reaction to Leech bites, Philippines

Nick Garbutt / Painted / Tiger Leech {Haemadipsa picta} waiting on leaf-edge for host, Lowland rainforest, Danum Valley, Sabah, Borneo.

Willem Kolvoort / Fish leech (Piscicola geometra) on reed stem, Holland

Willem Kolvoort / Medicinal leech (Hirudo medicinalis) amongst Rigid hornwort in an aquarium, Holland

Willem Kolvoort / Medicinal leech (Hirudo medicinalis) amongst Rigid hornwort in an aquarium, Holland

Willem Kolvoort / Medicinal leech (Hirudo medicinalis) amongst Rigid hornwort in an aquarium, Holland

Willem Kolvoort / Medicinal leech (Hirudo medicinalis) amongst Rigid hornwort in an aquarium, Holland

Willem Kolvoort / Medicinal leech (Hirudo medicinalis) amongst Rigid hornwort in an aquarium, Holland

Kim Taylor / Head of Leech {Pisciola sp} showing eyes

Kim Taylor / Leech {Glossiphonia sp} amongst water weed.

Kim Taylor / Leech {Helobdella stagnalis} showing internal structures

Kim Taylor / Leech {Herpobdella sp} showing internal structures

Mark Taylor / Tiger leech {Haemadipsa picta} on leaf. Borneo.

Kim Taylor / Horse Leech (Haemopis sanguisuga) attached to glass by their suckers. Captive

Kim Taylor / Horse Leech (Haemopis sanguisuga) attached to glass by their suckers. Captive

Mark Taylor / Brown Leech on human skin after sucking blood. Borneo.

Nick Garbutt / Tiger leech searching for host {Haemadipsa picta} Danum valley, Sabah, Borneo

Doug Wechsler / Tiger leech on human skin {Hirudinea} Sarawak, Lanjah, Malaysia

Adrian Davies / Horse leech {Haemopis sanguisuga} UK

Jason Smalley / Tropical leech {Hirundinea} held in hand at Leech farm, Wales, UK

Nature Production / Land Leech {Haemadipsa japonica} Japan

Nature Production / Asian Leech {Hirudo nipponica} Wakayama, Japan

Mark Moffett / Herpetologists donning pantyhose as a deterrent to Leeches, Tam Dao National Park, Vietnam

GEORGETTE DOUWMA / Leech on hand looking for soft skin {Hirudinea} Sabah Malaysia Indonesia

GEORGETTE DOUWMA / Leech on leaf stretching in response to body heat of prey {Hirudinea} Sabah Malaysia