Bence Mate / Leaf cutter ant (Atta sp) female worker carrying leaf to nest, with a smaller 'minor' ant riding. The minor's job is to protect her sister from parasitic flies. Costa Rica, December. Highly Commended,...

Kim Taylor / Bachacs / Leafcutter ants {Atta cephalotes} carrying sections of Cocoa leaf bearing 'riders' thought to ward off parasitic flies which would otherwise lay their eggs on the pieces of leaf. Trinidad, W...

David Fleetham / Great barracuda (Sphyraena barracuda) with three parasitic Copepods at end of upper jaw. Hawaii.

Lucas Bustamante / Brush footed butterfly (Lycorea sp.) caterpillar with parasitic wasp cocoons on silk threads, Yasuni National Park, Orellana, Ecuador.

Alan Murphy/ BIA / Northern Caracara (Caracara cheriway) chasing sub-adult with prey, Texas

Jordi Chias / Giant Manta (Manta birostris) with Remoras (Remora brachyptera) attached to both wings, offshore Santa Maria Island, Azores, Atlantic Ocean

Jordi Chias / Mobula / Chilean devil ray (Mobula tarapacana) with remora (Remora brachyptera) and Amberjacks (Serila dumerilli) Santa Maria Island, Azores, Atlantic Ocean

Solvin Zankl / Gall wasp (Cynips quercusfolii) emerging from the oak gall. Germany, October.

Alex Hyde / Parasitic fungus (Cordyceps militaris) fruiting body. This entomopathogenic fungus grows from an underground insect pupa or larva. Sherwood Forest National Nature Reserve. Nottinghamshire, UK. October...

Juergen Freund / Paralytic tick (Ixodes holocyclus) with engorged body on human hand, this species affects many species, Spectacled flying fox (Pteropus conspicillatus) among them and infects them with a toxin that ca...

Alex Mustard / Red eye medusa (Polyorchis penicillatus) with hitchhiking amphipods (Hyperia medusarum). Browning Pass, Vancouver Island, British Columbia, Canada. North East Pacific Ocean.

Alex Mustard / Large whip goby (Bryaninops amplus) with a parasitic copepod (with two trailing egg ribbons) perched on Red whip coral. Whale Rock. Fiabacet Islands, Misool, Raja Ampat, West Papua, Indonesia. Ceram S...