Eduardo Blanco / Pale burrower mayfly (Ephoron virgo), swarming in the millions on street at night, appearing like snow. Mayflies recently hatched. Tudela, La Ribera de Navarra, Navarre, Spain. August 2019. Finalist i...

Konrad Wothe / Slow motion clip of Mayflies (Ephemeroptera) swarming, Bavaria, Germany, May.

John Chan / Honey bees (Apis mellifera) swarming on a fence, Southern California, USA, December.

John Chan / Honey bees (Apis mellifera) swarming on an old gas tank and establishing a new nest site within, with some individuals beating their wings to create air circulation, Southern California, USA, February...

Solvin Zankl / Honey bee (Apis mellifera) swarming. Kiel, Germany, June.

Ingo Arndt / Tisza mayflies (Palingania longicauda) swarming, River Tisza, Hungary, June

Ingo Arndt / Mayflies (Palingenia longicauda) swarming, Tisza river, Hungary, June

Ingo Arndt / Mayfly (Palingenia longicauda) on water surface, swarming, Tisza river, Hungary, June

Alex Mustard / Vibrant Red Sea reef scene, with orange female Scalefin anthias (Pseudanthias squamipinnis) swarming in front of Fire coral (Millepora dichotoma) feeding on plankton brought to the reef by currents. R...

Bence Mate / Tisza mayflies (Palingania longicauda) swarming, River Tisza, Hungary

Mark Carwardine / Mass of insects swarming around light, Tefe, Amazonia, Brazil

Erlend Haarberg / Midges (Chironomus islandicus) swarming, Myvatn, Iceland, June