15-Sept The Browns and the Golden Rarities

Another brown sometimes confused with fritillaries is the wall brown. This also has many ‘eyes’ and was at one time called the London eye. This month its rich orange-brown colour gives it away and its ‘eyes’, rather than chequerboard markings, separate it from the fritillaries. In this case the males tend to be a little darker than the females due in part to the dark scent brands on their forewings. Identification gets a little more troublesome when meadow brown, gatekeeper and small heath are all flying in the same area as they do on Hutchinson’s bank. Size helps, with meadow browns being the largest and small heaths being the smallest. Gatekeepers are somewhere in between. Colour also helps with small heaths usually being the palest. They can even look grey when they settle. Gatekeepers tend to be an orange brown and meadow browns rather darker shades of brown. Unfortunately, when they all land and fold their wings they can all look very similar. All have a dark ‘eye’ on the underside of their forewing that is usually visible. If this ‘eye’ has two white dots inside it, it is a gatekeeper.

If it only has one it will be a meadow brown and if the dot is scarcely visible it is likely to be a small heath. Female gatekeepers tend to be larger and paler than the males and also lack the dark coloured sex brands on the male’s forewings.

Female meadow browns are more tricky as both sexes can vary so much. Although both may look faded and worn out this month, the males do still tend to look substantially darker. Dark as they are, they cannot be confused with ringlets which have now ceased flying altogether. Both sexes of the small heath are also variable but once again the females tend to be just a little larger. The males may only fly for a week and spend the whole of their adult life in one small patch of grass. In other months they are sometimes confused with skippers. However, skippers don’t have eyes and are usually a much richer brown colour. Small heaths also have a much more drunken way of flying than the speedy, controlled flight of skippers.

The last of the browns, the grayling, is unlikely to be encountered; but if it is, its size and silver grey undersides, which it shows at rest, immediately give it away. Once again the dark sex brands only on the males allow the sexes to be told apart. The females also tend to have larger, paler markings on their forewings. If both alight together the courting behaviour of the male with mark him out.

The last new butterfly to emerge in summer is the brown hairstreak. They are the largest of their group and for many the most beautiful. Their wings are chocolate brown with orange bands and they have small orange tails.

Their undersides are quite different, being almost golden with fine broken white lines. Unfortunately, they are one of the rarest and hardest butterflies to find. As they choose to lay their eggs on blackthorn, the winter trimming of hedges often spells disaster for any colony. The adults also choose to spend all their time in the tops of trees, especially ash trees. There they feed on honeydew and bask in the sunlight well away from the prying eyes of naturalists. Fortunately, this month the females deign to descend to lay their beautifully sculpted eggs which are covered in minute pentagonal cells. Once they have laid them on blackthorn twigs they may visit a bramble or thistle patch to feed before ascending again to the tops of trees. These rare descents only occur on the warmest days and perhaps may still be seen in Epping forest or Oaken wood. The so-called master trees they prefer are usually large ash trees set low in the landscape but still projecting above most of the other trees nearby.

Small coppers are far easier to find. They are also fussy, in this case preferring to lay their eggs on sheep’s sorrel or docks. They seem to do well on commons such as Mitcham common and are also happy to colonise motorway embankments. As there was a second brood last month and possibly another this month they are often seen at the beginning and end of September, but not usually in the middle.

There are also still one or two immigrants arriving in September of which landfalls of painted ladies tend to get the most attention. Even more spectacular, but far rarer, are the highly unpredictable invasions of clouded yellows. Early naturalists recorded seeing clouds of yellow butterflies approaching land from the sea, then being surrounded by saffron-coloured butterflies on the cliffs. Big invasions are called Edusa years after the clouded yellow’s old Latin name Colias edusa. Although so rare and unpredictable, their presence has been noted since the seventeenth century when they were first spotted in Peckham and Deptford. They can start arriving from May onwards. Being essentially a southern European or African species, it is only in perfect conditions that their numbers escalate.

If there are then favourable winds, these strong flyers can reach Britain, sea crossings presenting no obstacle to them. Early arrivals may lay five hundred eggs each and so, by late summer, their numbers can multiply to what is referred to as a “late invasion”. In such conditions they are often recorded along the North downs.

Clouded yellows are unmistakable sulphur yellow butterflies with golden yellow spots on their wings and black borders. They also have true green eyes and orange false ‘eyes’ on their wings. Telling males from females in the field is not easy although males, as so often, seem to fly faster. There is also an almost white ‘helice’ form which is supposed to make up a tenth of some populations although it never seems to be recorded in London.