Simon Colmer / Honeybee workers exchanging food - known as trophallaxis (Apis mellifera) Sussex, UK

Simon Colmer / Honey bee (Apis mellifera) workers exchanging food - known as trophallaxis, Sussex, UK

Piotr Naskrecki / Two slugs exchanging fluids, Atewa Range, Ghana

David Pattyn / Great Crested grebes (Podiceps cristatus) performing courtship dance and exchanging weed as part of ritual, La Dombes area, France, June

Simon Colmer / Honey bee (Apis mellifera) workers exchanging food - known as trophallaxis, Sussex, UK

Donald M. Jones / Limpkin (Aramus guarauna) pair exchanging snail, central Florida

Tui De Roy / Rockhopper Penguin (Eudyptes chrysocome) pair exchanging incubation duties, New Island, Falkland Islands

Heike Odermatt / Northern Gannet (Morus bassanus) pair exchanging nest material mid-flight, Helgoland, Germany

Scott Leslie / Tree Swallow (Tachycineta bicolor) pair exchanging food on the fly, Tobeatic Wilderness Area, Nova Scotia, Canada

Heidi & Hans-Juergen Koch / Honey Bee (Apis mellifera) pair right before exchanging food mouth to mouth, Bee Station at the Bavarian Julius-Maximilians-University of Wurzburg, Germany

Heidi & Hans-Juergen Koch / Honey Bee (Apis mellifera) pair exchanging food mouth to mouth, Bee Station at the Bavarian Julius-Maximilians-University of Wurzburg, Germany

Heidi & Hans-Juergen Koch / Honey Bee (Apis mellifera) pair exchanging food mouth to mouth, Bee Station at the Bavarian Julius-Maximilians-University of Wurzburg, Germany