I saw this in late July at Strumpshaw Fen. Swallowtail butterflies are different from all other British butterflies in a number of anatomical traits. Most obvious, the Swallowtail caterpillar possess a unique organ behind their heads, called the osmeterium. This is normally hidden as in the photograph, but this forked structure can be everted when the caterpillar is threatened, and emits smelly secretions containing terpenes. The adults are often tailed like the forked tail of some swallows, giving the insect its name. In Norfolk the Swallowtail lays its eggs on Milk Parsley which as far as I know is the only local source of food for these insects. The butterfly usually chooses the tallest plants to lay its eggs on. There is normally two broods of butterflies, the first one can be seen from late May to mid July and the second brood from mid August to late September. So this particular caterpillar would have come from the first brood of butterflies. Photograph taken by Susan McManus An extract from Wikipedia on Swallowtails. Swallowtail butterflies are large, colorful butterflies in the family Papilionidae, and include over 550 species. Though the majority are tropical, members of the family inhabit every continent except Antarctica. The family includes the largest butterflies in the world, the birdwing butterflies of the genus Ornithoptera. Swallowtails have a number of distinctive features; for example, the papilionid caterpillar bears a repugnatorial organ called the osmeterium on its prothorax. The osmeterium normally remains hidden, but when threatened, the larva turns it outward through a transverse dorsal groove by inflating it with fluid. The forked appearance of the swallowtails’ hindwings, which can be seen when the butterfly is resting with its wings spread, gave rise to the common name swallowtail. As for its formal name, Linnaeus chose Papilio for the type genus, as papilio is Latin for “butterfly”. For the specific epithets of the genus, Linnaeus applied the names of Greek heroes to the swallowtails. The type species: Papilio machaon honored Machaon, one of the sons of Asclepius, mentioned in the Iliad.
For anyone interested we have started a new Facebook Group, Norfolk Photography Group this will be open to anyone who has an interest in photography. There is no limitation of region, type of photography, ability of make of camera. The group will be open to comments , suggestions and constructive critique of images posted. We hope that this will be somewhere that members can post without feeling intimidated and provide a comfortable environment for all.
You can find this image and all previous images at our Photo Gallery. I always appreciate any images sent to me and will include these into these regular posts. So please look through your images and send me some for inclusion. If you can add a short description with the image all the better. Regards, Nick