Brimstone

(Gonepteryx rhamni)

Click on any picture to view a larger version

While a male Brimstone (on the left) can hardly be confused with any other butterfly, due to its sulphur-yellow colour, the female (right) can easily be confused with a Large White when in flight. The distinguishing feature is that a Brimstone has no dark spots or wing-tips but instead has distinctive circular markings, one on each wing. Also, the wings themselves have a scalloped shape rather than the continuous curves of a White
These images show the unusual dark-brown crescent-shaped structure where the wings join the body. Note that the male's body is yellow as well as its wings - the female is white, however. Note also the tendency of the female to pick up a greenish tinge by reflection from surrounding foliage

Neither male nor female ever sit at rest with their wings open, so under normal circumstances the taking of a photograph of the upper surface of the wing is almost impossible. The picture on the left is the nearest I've got - it's the result of pointing the camera in vaguely the right direction when one flew past and clicking the shutter! However, the female does sit with wings open when preparing to mate (centre). The male then flies up to her, so if you take enough pictures one of them will probably show him with wings open also - see at right! This male is rather battle-scarred - note that part of his wing to upper right is missing
The sequel to mating is, of course, egg-laying - from which emerges a caterpillar. These feed on buckthorn (rhamnus cathartica) and alder buckthorn (frangula alnus), as here	The caterpillar then turns into a chrysalis, with a very distinctive shape. If you think these examples have a less than natural background then you'd be quite correct! They are from two caterpillars we found on the alder buckthorn in our meadow and placed in a box for observation. If you look very carefully at the larger views you can just see the filament the caterpillar makes to secure itself. The crumpled object at the upper tip is the caterpillar's discarded skin
After 14 days one of the the chrysalises had changed colour to reflect that of the butterfly developing inside it	While the other had become very pale ....	Because it had hatched! Here we have a female, resting after emergence. If you look carefully you can see clear fluid beneath her, expelled as the wings were expanded

We then took her outside, whereupon she eventually flew away - initially alighting on a marjoram bush before disappearing into the meadow. Hopefully we'll see her again!
The second butterfly emerged the next day and as soon as we took the box outside it immediately flew, but only as far as a nearby finger! If you look carefully at the edge of the wings you will see a yellow colour, showing that it was a male despite having very pale underwings - confirmed when we saw it flying. It was not a strong flier but after a while it moved to the flower border to gain strength