14-Sept September’s Butterflies

Individual gatekeepers and speckled woods fly for about three weeks. With the days now starting to get cooler, others are just not encouraged to take to the wing quite as much. One advantage of the lower temperatures is that you are sometimes able to pick up a ‘sleeping’ butterfly in the early morning without it making any attempt to escape.

Even though numbers may be down it is still well worth looking for butterflies on warm sunny days as second, third and even fourth broods may now be emerging in their brightest livery. This is especially true for the large, colourful species we tend to see in gardens. Many of these also have a habit of returning to the same place to feed each day.

The butterflies most associated with late summer are the peacocks, red admirals, painted ladies, commas and speckled woods, all of which we tend to see in our gardens. Others such as meadow brown and gatekeepers tend to get noticed more in grassy areas. For a variety of reasons some of these may have by now built up substantial populations. For some other rarer species such as the brown hairstreak, Adonis blue and the clouded yellow this can also be an important month and there may be a better chance of seeing them. Although most of the skippers seem to have disappeared last month it is still possible to find the dingy, grizzled and perhaps even a silver-spotted skipper this month, but only in the first week. The first two species can be found on Hutchinson’s bank.

The much rarer silver-spotted skipper, which only lives for a fortnight as an adult, is best looked for on steep, well grazed, chalky, south facing slopes such as Box Hill. The ever present whites i.e. large, small and green-veined, all start to disappear in early September. It is also worth looking out for late broods of large whites as these often have much more intense markings than earlier broods.

The blues generally tend to be more a feature of the first part of the month. Holly, chalk hill and brown argus can all possibly still be seen. The small blue is only likely in the first week but the Adonis blue may be flying the whole month. Like so many other butterflies, it has very precise food requirements as well as a complicated life cycle involving ants. In this case it will only lay its eggs on horseshoe vetch which, in our area, seems to be restricted to one or two places of perfect chalk downland. Even then the turf has to be exactly the right height and there must be bare chalky scrapes for the females to bask whilst waiting for males to visit them.

For us, the hunt is well worthwhile as the blue of the Adonis blue is arguably more intense than any other animal or plant in London. It is often described as electric blue and is not unlike the famous blue morpho butterflies of South America. Their colour has been described as the “bluest blue in the world”. The females are a slightly disappointing chocolate colour. If the light is poor and colour is not enough to identify the males they also have a white fringe to their wings which has tiny black lines crossing it at regular intervals. Discrete populations used to exist in the old chalk pits along the North Downs but now it would be better to look for them on Hutchinson’s bank or possibly Ranmore Common. A rare variant with thick black radiating lines on its undersides rather than the usual spots has been found in the latter location.

Any large congregation of Vanessids and other large colourful butterflies on late summer perennials in gardens is one of the most memorable sights of the month. Typical species to be seen include red admiral, peacock, painted lady, large white, comma and small tortoiseshell.

The numbers of small tortoiseshells may possibly be swollen this month by recent immigrants. Many of them are even more brightly coloured than usual as they have recently emerged from late broods and stand out against any tattered, faded individuals from earlier hatchings. Red admirals were known as red admirables in the eighteenth century and can reach numbers of fifty or more on favoured plants in large gardens such as Wisley.

Peacocks are best looked for where there are rotting windfall fruit on the ground, especially pears. They have larger ‘eyes’ on their wings than any other British species in order to startle would-be predators. This is especially true when they open their wings, which make a slight noise as they move and reveal two more ‘eyes’. If this does not do the trick they then close their wings which, being virtually black underneath, instantly hides the ‘eyes’ giving the impression they have disappeared.