Roman Willi / Asian bush mosquito (Aedes japonicus) feeding on human blood, Lucerne, Switzerland. July.

Doug Wechsler / Tachnid fly / Bristle fly (Juriniopsis adusta) resting on tree bark, Pennsylvania, USA. August.

Doug Wechsler / Bristle fly (Vibrissina sp.) parasitising Saw fly (Arge coccinea) larva, Wissahickon Valley Park, Pennsylvania, USA. July.

Doug Wechsler / Bristle fly (Gonia sp.) portrait, Pennsylvania, USA. April.

Doug Wechsler / Bristle fly (Gonia sp.) portrait, Pennsylvania, USA. April.

Doug Wechsler / Tachinid fly (Archytas metallicus) resting on a hand, Wissahickon Valley Park, Pennsylvania, USA. July.

Doug Wechsler / Flesh fly (Sarcophagidae) investigating a Tachinid fly (Archytas metallicus) on human skin, Wissahickon Valley Park, Pennsylvania, USA. July.

Nick Upton / Dark-palped Melinda / Bluebottle fly (Melinda viridicyanea) resting on a leaf in garden, Wiltshire, UK. August.

Nick Upton / Giant tachinid / Yellow-faced fly (Tachina grossa) nectaring on Hemp agrimony (Eupatorium cannabinum) flowers, Strumble Head, Pembrokeshire, Wales, UK. August.

Nigel Cattlin / Recovering Fly strike wound on the hind quarters of a Friesian sheep, caused by feeding of Blow fly (Calliphoridae) maggots, Gloucestershire, UK. August.

Gil Wizen / Female Tick fly (Forcipomyia sp.) attached to and feeding on a stick insect in the rainforest, Jatun Sacha Biological Station, Napo province, Amazon basin, Ecuador. Focus-stacked image.

Chris Mattison / Tachinid fly (probably Tachina fera) feeding on Ivy (Hedera sp.) flowers, Wales, UK. October.

Doug Wechsler / Linden lacebug (Gargaphia tiliae) with eggs, with parasitic fly larvae and mite on eggs, Pennsylvania, USA. June.

Doug Wechsler / House fly (Muscidae sp.) feeding from earthworm (Lumbricidae sp.), Philadelphia, Pennsylvania, USA. June.

Doug Wechsler / Parasitic fly (Calodexia sp.), an army ant associate, parasitizing insects escaping from army ants (Eciton sp.), La Selva Biological Station, Costa Rica.

Paul Williams / Carrion fly on the parasitic plant Rafflesia pricei flower, Mount Kinabalu, Borneo, May, 2013. Filmed for the BBC series 'Wonders of The Monsoon'.

Paul Williams / Carrion fly on the parasitic plant Rafflesia pricei flower, Mount Kinabalu, Borneo, May, 2013. Filmed for the BBC series 'Wonders of The Monsoon'

Bruce Thomson / Eastern bentwing / Eastern long fingered bat (Miniopterus orianae oceanensis) hibernating cluster in cave, one bat with bat fly (Hippoboscoidea) Girraween National Park, Queensland, Australia.

Bruce Thomson / Eastern bentwing / Eastern long fingered bat (Miniopterus orianae oceanensis) hibernating cluster in cave, one bat with batfly (Hippoboscoidea) Girraween National Park, Queensland, Australia.

Bruce Thomson / Eastern long fingered bat (Miniopterus orianae oceanensis) roosting in a cluster on roof of a cave during day, a few ectoparasitic batflies (Hippoboscoidea) are visible, Girraween National Park, Queen...

Bruce Thomson / Common vampire bat (Desmodus rotundus) family group infested with ectoparasitic batflies (Hippoboscoidea) roosting in cave aven / vertical shaft, Yucatan Peninsula Mexico

Alex Hyde / Swift Louse Fly (Crataerina pallida) an obligate haematophagous parasite of the Common Swift (Apus apus). Note the atrophied vestigial wings. Photographed on a white background. Devon, UK. July.

Solvin Zankl / Great Frostspanner (Erannis defoliaria) caterpillar covered in parasitic fly maggots.

Solvin Zankl / Great Frostspanner (Erannis defoliaria) caterpillar covered in parasitic fly maggots.

Nick Upton / Parasite fly / Tachinid fly (Prosena siberita) with distinctive long proboscis, a parasite of chafer beetles, resting on photographer's leg, Pewsey Downs, Wiltshire, UK, July.

Nick Upton / Black deerfly (Chrysops sepulcralis) a nationally scarce species in the UK of boggy habitats, preparing to suck blood from photographer's hand near a pond margin, Dorset heathland, UK, July.

Nick Upton / Heath bee fly (Bombylius minor) hovering near nest burrows of host bees (Colletes sp.) in a sandy clay bank, Dorset heathland, UK, July.

Nick Upton / Kleptoparasitic Silver-fronted satellite fly (Metopia argyrocephala) approaching the nest burrow of a Bee wolf (Philanthus triangulum) a host species for its larvae, Dorset heathland, UK, July.

James Dunbar / Slow motion clip of a Beefly (Bombyliidae sp.) laying eggs by flicking them into the nest of a solitary bee, UK, April.

Nigel Cattlin / Female parasitoid wasp (Aphaereta debilitata) a parasite of shore fly larvae, a pest in lettuce crops

Andy Sands / Tachnid fly (Eriothrix rufomaculata) a common Tachnid fly found in damp meadows photographed at dawn covered in dew, Hertfordshire, England, UK, July - Focus Stacked

Rod Williams / Tachinid parasitic fly (Thelaira nigripes) Sutcliffe Park Nature Reserve, Eltham, London, England, UK, June.

Rod Williams / Tachinid parasitic fly (Blepharipa pratensis) Rare species, new to London area Beverley Court Gardens, Lewisham, London, England, UK. May.

Rod Williams / Tachinid parasitic fly (Blepharipa pratensis) Rare species, new to London area. Beverley Court Gardens, Lewisham, London, England, UK, May.

Doug Wechsler / Tachinid fly (Juriniopsis adusta) on fern, Morris Arboretum, Pennsylvania, September.

Nick Upton / Conopid / Thick-headed fly (Myopus pellucida) a parasite of mining bees, sunning on a Honeysuckle leaf in a garden, Wiltshire, UK, April.

Nick Upton / Dotted bee fly (Bombylius discolour) female hovering while flicking its tail down to "bomb" eggs onto the ground near the nest entrance of a Yellow-legged mining bee (Andrena flavipes), its main host,...

Guy Edwardes / Thick-headed fly or Wasp fly (Myopa sp.), pair mating, Westhay, Somerset Levels, Somerset, England, UK, June.

Ramon Navarro / Common house mosquito (Culex pipiens) feeding on human blood before flying off, mosquito becoming engorged with blood. Controlled conditions. Sequence 4 of 4.

Ramon Navarro / Common house mosquito (Culex pipiens) feeding on human blood, mosquito becoming engorged with blood. Controlled conditions. Sequence 3 of 4.

Ramon Navarro / Common house mosquito (Culex pipiens) feeding on human blood, mosquito becoming engorged with blood. Controlled conditions. Sequence 2 of 4.

Ramon Navarro / Common house mosquito (Culex pipiens) feeding on human blood, mosquito becoming engorged with blood. Controlled conditions. Sequence 1 of 4.