Ralph Martin/ BIA / Oldworld Swallowtail (Papilio machaon) wing, Baden-Wurttemberg, Germany

Peter Schwarz/ BIA / Oldworld Swallowtail (Papilio machaon) butterfly, Hesse, Germany

Jussi Murtosaari / Apollo butterfly (Parnassius apollo) in flight, Foglo, Ahvenanmaa / Aland Islands, Finland, July.

Silvia Reiche / Oldworld Swallowtail (Papilio machaon) caterpillar on fennel, Netherlands

Jussi Murtosaari / Mountain Apollo (Parnassius apollo) in flight, southwest Finland, February, July.

Jussi Murtosaari / Mountain Apollo butterfly (Parnassius apollo) male flying across road, Aland Islands, Finland, July.

Thomas Marent / Oldworld Swallowtail (Papilio machaon) caterpillar, Switzerland

Paul Harcourt Davies,Paul Harcourt Davies / Common Swallowtail butterfly (Papilio machaon) backlit showing wing structure. Podere Montecucco, Orvieto, Umbria, Italy, October

Paul Harcourt Davies,Paul Harcourt Davies / Apollo butterfly (Parnasius apollo) feeding on flower, Mount Terminillo, Rieti, Lazio, Italy, July 2011

Terry Whittaker / 2020VISION / Swallowtail Butterfly (Papilio machaon britannicus) on hawkbit flower. Strumpshaw Fen, Norfolk, June.

Terry Whittaker / 2020VISION / Swallowtail Butterfly (Papilio machaon britannicus) on hawkbit flower. Strumpshaw Fen, Norfolk, June.

Alex Hyde / Common Swallowtail butterfly (Papilio machaon) resting on Meadow Clary (Salvia pratensis) flowers, on a white background. Nordtirol, Tirol, Austrian Alps, Austria, 1700 metres altitude, July.