Enrique Lopez-Tapia / Traditional outfit of Melanesian man, Tanna Island, Tafea Province, Vanuatu, September 2008.

Nick Upton / Close up of female captive bred Water vole (Arvicola amphibius) being sexed before release into wild during reintroduction project, Derek Gow Consultancy, near Lifton, Devon, UK, March. Model release...

Nick Upton / Testicles of a sedated young male Pygmy goat (Capra aegagrus hircus) that has just been castrated in an operating theatre, Wiltshire, UK, September 2014. Model released.

Nick Upton / Close up of male captive bred Water vole (Arvicola amphibius) being sexed before release into wild during reintroduction project, Derek Gow Consultancy, near Lifton, Devon, UK, March. Model released.

Nick Upton / Rebecca Northey sexing male captive reared Water vole (Arvicola amphibius) during breeding programme to supply reintroduction project, Derek Gow Consultancy, near Lifton, Devon, UK, March 2014. Model...

Steve O. Taylor (GHF) / Chimpanzee (Pan troglodytes) standing on hind legs looking out at visitors, J.A.C.K. Sanctuary (Jeunes Animaux Confisqus au Katanga / Young animals confiscated in Katanga), Lubumbashi, Katanga, Democr...

Yukihiro Fukuda / Feral domestic rabbit (Oryctolagus cuniculus) male and female resting together, Okunojima Island, also known as Rabbit Island, Hiroshima, Japan.

Anup Shah / African elephant (Loxodonta africana) male unsuccessfully mating with a female. Maasai Mara National Reserve, Kenya. Feb 2012.

Nick Upton / Bat scientist inspecting the genitalia of a male Greater horseshoe bat (Rhinolophus ferrumequinum) during a winter hibernation survey in an old Bath stone mine, Wiltshire, UK, February. Model released...

Alex Mustard / High magnification of reproductive apparatus of pair of Lined nembrotha nudibranchs (Nembrotha lineolata) mating. Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Oce...

Enrique Lopez-Tapia / Insect, possibly a Parasitoid wasp (Braconidae) female with extremely long ovipositor, backlit on leaf. Canamina forest. Cantanhez National Park, Guinea-Bissau.

Anup Shah / Long-tailed macaque (Macaca fascicularis) sub-mature male examining his genitalia. Bako National Park, Sarawak, Borneo, Malaysia. Mar 2010.

John Cancalosi / Leopard slug (Limax maximus) pair mating, white male organs exchanging sperm, hermaphroditic species, New York, USA, August.

John Cancalosi / Bluetick coonhound, male panting, Pennsylvania, USA, June.

Will Watson / Female Great diving beetle (Dytiscus circumflexus) view of underside with cloacal sperm plug from previous mating, UK, captive.

Anup Shah / Olive baboon (Papio anubis) male watching with curiosity. Masai Mara National Reserve, Kenya. Taken with remote wide angle camera.

Ann & Steve Toon / Wild elephant (Loxodonta africana), vas deferens, removed during keyhole surgery in the bush. Private game reserve in Limpopo, South Africa, April 2011. Winner of the IUCN grant in the Melvita Natu...

Jeff Rotman / Close up view of male reproductive organ 'Claspers' of Whitetip Reef Shark (Triaenodon obesus) Cocos Island, Costa Rica, Pacific Ocean.

Ingo Arndt / Carpet Python (Morelia spilota) hemipenis, Australia

Robert Valentic / Close up of everted hemipene (bi-lobed male reproductive organ) of Northern death adder {Acanthophis praelongus} Northern Territory, Australia

Staffan Widstrand / African bush elephant, (Loxodonta africana) penis, Zimanga Private Nature Reserve, KwaZulu Natal, South Africa

Denis-Huot / Lion (Panthera leo), male resting, showing penis and testicles, Kenya

Hermann Brehm / Lion (Panthera leo) pair about to mate, male penis visible, Tanzania.

Albert Lleal / Algae (Characeae) male reproductive organ, Cap de Creus, Catalonia, Spain

Albert Lleal / Algae (Characeae) male reproductive organs, Cap de Creus, Catalonia, Spain

Albert Lleal / Algae (Characeae) male reproductive organs, Cap de Creus, Catalonia, Spain

Roland Seitre / Red kangaroo (Macropus rufogriseus) penis, Australia. Captive.

Andy Sands / Kleptoparasitic wasp (Gasteruption jaculator) female, roosting on grass stem, Hertfordshire, England, UK. July. Focus stacked.

Nick Upton / Wild carrot wasp (Gasteruption jaculator) female, laying eggs in the nest of a Common Yellow-face bee (Hylaeus communis) in an insect hotel, Wiltshire garden, UK. July.

Nick Upton / Wild carrot wasp (Gasteruption jaculator) female, a parasite of solitary bees and wasps, hovering by an insect hotel in search of host nests, Wiltshire garden, UK. June.

Nick Upton / Wild carrot wasp (Gasteruption jaculator) female, laying eggs in the nest of a Common Yellow-face bee (Hylaeus communis) in an insect hotel, Wiltshire garden, UK. July.

Nick Upton / Wild carrot wasp (Gasteruption jaculator) female, a parasite of solitary bees and wasps, visiting an insect hotel in search of host nests, Wiltshire garden, UK. June.

Nick Upton / Wild carrot wasp (Gasteruption jaculator) female, a parasite of solitary bees and wasps, visiting an insect hotel in search of host nests, Wiltshire garden, UK. June.

Harry Collins / African bush elephant (Loxodonta africana) juvenile walking near adult. Then the animal stops and raises its trunk. Maasai Mara, Kenya, Africa. November. Endangered.

Noemie Stroh / Tracking shot of a Bottlenose dolphin (Tursiops) male swimming along sandy seabed. The animal is displaying its penis and playing, rubbing itself in the sand. Sha'ab El Erg, Red Sea.

Nigel Cattlin / Parasitoid wasp (Aphidius spp.) female, about to lay eggs in Peach potato aphid (Myzus persicae) with ovipositor pointing forward, England, UK.

Doug Wechsler / Signal fly (Pseudotephritis approximata) female, laying eggs in tree bark, Camp Woods Preserve, Pennsylvania, USA. August.

Doug Wechsler / Pigeon horntail (Tremex columba) female, laying eggs on tree bark, Camp Woods Preserve, Pennsylvania, USA. September.

Doug Wechsler / Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) female ovipositing, the translucent membrane helping to push the threadlike ovipositor deep into the wood of a dead tree, Camp Woods Preserve,...

Doug Wechsler / Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) female laying eggs in trunk of dead tree, Camp Woods Preserve, Pennsylvania, USA. September.

Doug Wechsler / Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) female laying eggs in trunk of dead tree, Camp Woods Preserve, Pennsylvania, USA. September.

Doug Wechsler / Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) female ovipositing, showing the translucent membrane used to push the threadlike ovipositor deep into the wood of a dead tree, Camp Woods Prese...

Doug Wechsler / Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) female ovipositing, the translucent membrane helping to push the threadlike ovipositor deep into the wood of a dead tree, Camp Woods Preserve,...

Ripan Biswas / Giant ichneumon wasp (Rhyssa persuasoria) using its ovipositor to lay eggs, Buxa tiger reserve, West Bengal, India.

Doug Wechsler / Female Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) wiping ovipositor with hind legs after having parasitized larva of horntail wasp. Pennsylvania, USA. September.

Doug Wechsler / Female Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) ovipositing by parasitizing larva of horntail wasp inside trunk of dead tree using ovipositor consisting of sheath with sharp point for...

Doug Wechsler / Female Long-tailed giant ichneumonid wasp (Megarhyssa macrurus) ovipositing by parasitizing larva of horntail wasp inside trunk of dead tree using ovipositor consisting of sheath with sharp point for...

Andy Sands / Dune villa fly (Villa modesta), female, landing on bare sand, quivering tail to gather small sand grains in cloaca later enabling them to disperse their eggs better from flight position. Cornwall,...

Franco Banfi / Male sperm whale (Physeter macrocephalus) close up, showing extended penis, Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit. February.

Franco Banfi / Two Sperm whales (Physeter macrocephalus), males, showing extended penis, Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit. February.

Tui De Roy / Pair of Green sea turtle (Chelonia mydas) washed up on beach while mating, Quinta Playa, Isabela Island, Galapagos Islands, Ecuador. Pacific ocean.

Jiri Lochman / Gasteruptid wasp (Gasteruption sp.) female, resting on a leaf, Mount Gibbs Nature Reserve, Western Australia. March. (Gasteruptiidae)

Jiri Lochman / Gasteruptid wasp (Gasteruption sp.) female, foraging among Eucalyptus (Eucalyptus sp.) flowers, Mount Gibbs Nature Reserve, Western Australia. March. (Gasteruptiidae)

Jiri Lochman / Parasitic wasp (Megalyra sp.) female, on tree bark, South West forests, Western Australia. March. (Megalyridae)

Jiri Lochman / Parasitic wasp (Megalyra sp.) female, on tree bark, South West forests, Western Australia. March. (Megalyridae)

Jiri Lochman / Parasitic wasp (Megalyra sp.) female, on tree bark, South West forests, Western Australia. March. (Megalyridae)

Jiri Lochman / Parasitic wasp (Megalyra sp.) female, on tree bark, Chaelundi National Park, New South Wales, Australia. September. (Megalyridae)

Jiri Lochman / Gasteruptid wasp (Gasteruption sp.) female, exhibiting full length of its strikingly long ovipositor while feeding on a Waxflower (Chamelaucium sp.), Dryandra Forest, Western Australia. October. (Gast...

Marie Lochman / Gasteruptid wasp (Hyptiogaster sp.) female, feeding on a Waxflower (Chamelaucium sp.) flowers, Kalbarri National Park, Western Australia. August. (Gasteruptiidae)

Marie Lochman / Gasteruptid wasp (Gasteruption sp.) female, feeding on a Myrtle (Myrtus sp.) flower Bindoo Hill Nature Reserve, Western Australia. September. (Gasteruptiidae)

Marie Lochman / Gasteruptid wasp (Gasteruption sp.) female, feeding on a Waxflowers (Chamelaucium sp.), Dryandra Forest, Western Australia. October. (Gasteruptiidae)

Konrad Wothe / Crown wasp (Stephanidae) on tree bark in rainforest, showing ovipositor, Panguana Reserve, Huanuca province, Amazon basin, Peru.

Roland Seitre / Close up of the male genitalia of Ostrich (Struthio camelus), South Africa. Captive

Doug Gimesy / Grey-headed flying-fox (Pteropus poliocephalus) male courtship / mating behaviour with female including licking her genitalia, then bickering, before male grooms his own penis, Yarra Bend Park, Victor...

David Tipling / Grey seal (Halichoerus grypus) mating pair, Horsey, Norfolk, UK. November.

Paul Harcourt Davies / Female Great green bush-cricket (Tettigonia viridissima) nymph, with its ovipositor fully developed but not its wings, resting on leaf, Umbria, Italy. November.

Doug Wechsler / Close up of female Periodical cicada (Magicicada sp.) ovipositor, Philadelphia, Pennsylvania, USA. May 2021

Edwin Giesbers / Vet doing a check-up on Eurasian lynx (Lynx lynx) kitten, aged five weeks, breeding and reintroduction program, Germany. Captive. July.

Doug Perrine / Day octopus (Octopus cyanea) female jetting away during mating while the male's hectocotylus arm on the right is still extended into her mantle, Hoover's Reef, North Kona, Hawaii. Central Paci...

Joao Burini / Ichneumonid parasitoid wasp (Ichneumonidae) on leaf, Southeastern Atlantic Forest, Mantiqueira Mountain Range, Sao Francisco Xavier, Sao Paulo, Brazil.

Jiri Lochman / Short-beaked Echidna (Tachyglossus aculeatus acanthion) female - detail of the cloaca and the pouch area, Brookton Highway, Wheatbelt Region, Western Australia,- November.

Ripan Biswas / Parasitic wasp (Xanthocryptus novozealandicus) Buxa Tiger Teserve, India.

Pete Oxford / Dani tribe man with penis gourd / koteka. Budaya village, Suroba, Trikora Mountains, West Papua, Indonesia. October 2020.

Pete Oxford / Dani tribe man with penis gourd / koteka. Budaya village, Suroba, Trikora Mountains, West Papua, Indonesia. October 2020.

Pete Oxford / Dani tribe man with penis gourd / koteka tied to cane belt, Budaya village, Suroba, Trikora Mountains, West Papua, Indonesia. March 2018.

Pete Oxford / Dani tribe man, with penis gourd / koteka. Budaya village, Suroba, Trikora Mountains, West Papua, Indonesia. March 2018.

Pete Oxford / Dani tribe people, woman and man with penis gourd. Budaya village, Suroba, Trikora Mountains, West Papua, Indonesia. March 2018.

Nick Upton / Ichneumon wasp (Ichneumonidae / Pimplinae) female with a long ovipositor grooming its abdomen while sunning on a Dogwood leaf on a chalk grassland slope, Bath and Northeast Somerset, UK, May.

Etienne Littlefair / Irwin's turtle (Elseya irwini), adult male resting. Note the sediment disturbance to the rear of the turtle is caused by expulsion of water via cloacal respiration. North Johnstone River, downstre...

Ingo Arndt / Honey bee (Apis mellifera), dead drone at nest entrance. Visible genitals/penis, Germany.

James Dunbar / Hoverfly (Epistrophe grossulariae) attempting to lay eggs amongst aphids. Ovipositor visible, April, UK

James Dunbar / Hoverfly (Epistrophe grossulariae) taking off from flower and landing again, April, UK

Will Watson / Male Vervet monkey (Chlorocebus aethiops) eating a mango fruit, showing blue scrotum, Samburu Lodge, Kenya. January.

Andy Sands / Ichnumen wasp (Lissonata Sp.) female resting on a Bluebell flower, Hertfordshire, England, UK, April - Focus Stacked