Picture: a clouded yellow butterfly on common fleabane. Click here to see more September butterfly and insect photos. For more information on butterflies and moths see the Butterfly Conservation website.
There are still quite a variety of insects to see in September, but sightings are now fairly infrequent. An exception is around flowering ivy, which attracts quite large numbers of insects to its late supply of nectar. The same can be true of other late flowering shrubs such as Russian vine and snowberry, and wildflowers such as michaelmas daisies. Especially fond of these are honeybees, wasps, and hoverflies and flies of various kinds.
Honeybees spend the winter in hives, feeding on stored honey, and so can be out and about for as long as there are flowers for them to gather nectar from. In favoured spots the air is still filled with their very summery hum.
With bumble bees it is only the already-mated new queens who survive the winter, to found a colony next year. You see these in September, often flying very close to the ground, feeding up for their winter hibernation and looking for a hole in the ground to spend it in. There is something wonderfully imperious about their buzzing as they navigate around you. There may also still be a few bumble bee workers on the wing early in the month, while those of the common carder bee, identified by the ginger hair on their thorax, can be seen into October.
One solitary bee that is still around is the ivy mining bee, which looks like a neater version of the honeybee (the males smaller than honeybees, the females a bit bigger). It synchronises its lifecycle with the flowering of ivy, and so is at its best this month, Numerous males of this species can be seen flying frantically around ivy flowers, looking for females, and you also find colonies of their nest holes in thinly-vegetated south-facing banks (sometimes garden lawns), where you can see both females entering and leaving the holes, and males swarming around hoping to mate with them. At least around ivy they might be mistaken for honeybees, but crucially do not hum, not being social animals. Only identified in southern Europe in 1993, and first seen in the UK in Dorset in 2001, this charming invader has been spreading steadily north and has now reached the Midlands.
The wasps you see are redundant workers, who feed on rotting fruit before dying off: the jam in our cream teas provides an alternative, as do ivy flowers, which are actually one of the most reliable places to see them these days. These workers are on the wing all month and in recent memory, they were a major nuisance in pub gardens and at picnics in the late summer. Numbers have declined rapidly in the last few years, however, and since 2021 there have been shockingly few of them. As with bumble bees, only the queens survive the winter, finding a cosy nook to hibernate in, before founding a new colony in the spring. Somewhat larger than ordinary wasps, they are a slightly scary sight, but if you see one, don't swat it: it carries the future of its species.
Hoverflies can also still be seen, though numbers are very much reduced from their summer highs. Particularly around ivy you can still see a wide variety of them, however, including drone flies and syrphus types. Many look exactly like bees - a deliberate evolutionary adaptation to avoid predation - though the hornet-mimic hoverfly takes that one step further with a very convincing imitation of the insect after which it is named.
Also much reduced, but still encountered from time to time, are various different kinds of tiny flying insects too small for non-experts to identify, as well as gnats, who keep going all winter, appearing in small swarms on still, sunny days. The tiny black creatures you see on dandelions and hawkbits are pollen beetles.
Surprisingly, some insects are only just emerging in September. Seven-spot ladybirds - the classic red ones with black spots that everyone recognises - are metamorphosing into adults in late August and early September, having grown from eggs laid in May. They will feed for a while and then find a cosy place to spend the winter (often in groups) in plant debris, leaf litter or wooden window frames, waking up in spring to mate and lay eggs.
New green shield bug adults also emerge in September, though they are well camouflaged against plants and so hard to spot. Easier to see are brown dock bugs, whose adults appear in August and are still around in September: they feed on blackberries and so can often be found on bramble bushes. Both of these species lie dormant over the winter and lay eggs in May, just like ladybirds.
You can still see crane flies in grassy fields (they seem to actually pick up a bit in September after being more scarce in August): you often notice them as they dart away from your feet as you walk. Particularly in the first half of the month, the same is true of grasshoppers and crickets. At the same time ants are still busy searching for food across grassland and bare ground; once the weather turns colder they seal up their nests for winter. Snails and other garden fauna get much scarcer as the month goes on, but can still pop up when you least expect them.
Spiders actually become more prominent this month, as orb weaver spiders make their classic webs of concentric circles in our gardens. The ones you see are females (the males are much smaller), who have mated and made a silken cocoon in which to lay their eggs. They will guard these until they die of cold later in the autumn and the eggs will then go on to hatch in the spring. The web doesn't stay sticky for long so the spider will rebuild it every day or two, consuming the old web as she goes - a task that takes as little as half an hour.
This is also the time of year when you may notice alarmingly large house spiders in your house. Contrary to popular myth they do NOT come inside at this time of year to escape the cold - or not only. They are for there all along, out of sight and manning webs in obscure corners. But at this time of year males come out of hiding to search for a mate, which is why you encounter them on the stairs or walking across your living room. Please leave them alone: they will not harm you, and are as reluctant to see you as you are to see them (though do help them out of baths, where they sometimes get stuck looking for water). They have their own predators - large cellar spiders that we thankfully never see.
The morning dew also reveal the threads that money spiders use to "balloon" out across fields: they attach their threads to a blade of grass and then launch into the sky using air currents. They do this in order to avoid mating with siblings. One field can have millions of threads.
One other class of insect that is surprisingly active in September is the dragonfly. Species still on the wing include the common darter (very common this month, the males red and the females more yellowy), the beautiful green-blue southern hawker, and the blue and chocolate-coloured migrant hawker. All these can be seen till late in the month around ponds and streams, as well as further afield. Just occasionally very early in the month you may see a common blue damselfly, while the willow emerald damselfly, first recorded in East Anglia in 2009 and now spreading across the country, can be on the wing into October. On still water you may still see pondskaters.
Butterflies and day-flying months
Butterflies become much scarcer in September, but you can still see some when the sun shines and there are flowers for them to feed on. White butterflies are on the wing until late in the month, and at the start of the month can still be very numerous. When they stop long enough to be identified (which is rarely) they often seem to be small whites, though large or green-veined whites are possible too. Speckled woods also reliably last till later in the month.
A new generation of commas and small tortoiseshells may appear in late August and early September if the summer has been good, though they are usually not very numerous. These are the offspring of the generation that appeared in July and have only one aim, which is to find a place to hibernate (technically, diapause: the butterflies switch off their metabolism altogether but can switch it on again immediately if disturbed). They are therefore not on the wing for long.
Commas are particularly hard to see because with their wings closed they look like a dead leaf - the perfect camouflage for this time of year. If the summer was a poor one, this generation is skipped altogether and the July one goes straight into diapause. In both cases the butterflies then emerge in March to mate. The occasional peacock or brimstone, also overwintering species, is also possible, particularly early in the month.
Another butterfly that might just pop up at any time of the month is the red admiral: in 2017 and 2023, indeed, they were the most common September butterfly, and in 2021 they were also quite widespread. Though a migrant which should be on its way south by now (if you are down at the coast or on the South Downs you sometimes see them flying straight and fast out to sea), some even manage to survive the winter, emerging on warm days in January, February or March. There is as yet no evidence that they then go on to mate in spring, but they seem to be on their way to becoming another diapausing butterfly.
All of these overwintering butterflies - comma, small tortoiseshell, peacock and particularly red admirals - may turn up on flowering ivy late in September or even into October, long after you have concluded that you have seen your last butterfly of the year.
Other migrants you might see in the first three weeks of the month include painted ladies and clouded yellows. It used to be thought that painted ladies simply died off at the end of the summer, but science has now established that they migrate back south again to their winter breeding grounds in Morocco (or even, it seems, Sub-Saharan Africa, using high altitude winds.
As for the clouded yellows, this can be the best month to see them, since now you get the offspring of migrants who arrived earlier in the summer. You may therefore see several in one place, rather than just one flying past at speed, as is more the norm in August. The coast of Sussex seems to be a particularly good place to see this, Lancing Ring, Mill Hill near Shoreham-by-Sea, the Ouse Estuary Nature Reserve near Newhaven, the downs around High & Over Hill, and Beachy Head all being possible spots.
On grassland you may still see meadow browns early in the month (occasionally a bit later), while common blues can turn up in the same habitat as late as the third week. The first half of the month can still be a good time for adonis blues, if you are lucky enough to find a colony of them. They live on south-facing downland slopes, for example on the lower slopes of Ranmore Common near Dorking or in Mill Hill Reserve near Shoreham-by-Sea, and produce a second generation from mid August onwards.
Some chalk hill blues may just also survive on south-facing downland into the first week, and the same is true of holly blues some years. In 2020, 2022 and 2023 long-tailed blues, a continental species, made incursions onto the south coast - with sightings near Kingsdown and Seaford in 2020, on Whitehawk Hill in Brighton and the West Worthing seafront in 2022 , and near Lancing, Brighton and Eastbourne in 2023. An occasional brown argus is possible on downland in the first week of September.
Tiny small heath butterflies can in theory be seen on downland all month, but are most likely right at its start. You may just see a small copper in the first half of the month and they can produce a further very small generation towards its end. Walls, coastal butterflies in our part of the world, can also produce a third generation late the month on the Sussex and Kent coasts, which then lasts into October. In flight they look a bit like a meadow brown in a hurry.
Early in the month (till the fourth week in 2021) you may see some surviving brown hairstreaks on and around blackthorn bushes, but this is a very elusive butterfly that you are only likely to spot in a site where it is known to be present. Also just about possible in the first half of the month is a well camouflaged grayling on the Surrey heathlands.
Day-flying moths are largely gone, but you may see one or two, particularly at the start of the month. These include the tiny white veneer moths (or perhaps the brown rush veneer which hides among dead bracken), and maybe a silver Y. I have also three times seen hummingbird hawkmoth and common plume moths in September, twice a snout, and once each a Jersey tiger, yellow shell, yellow belle, mint month and straw-barred pearl.
Lambs, bullocks and the deer rut
The amount of livestock in the fields reduces as the month goes on, but it is hard to put your finger on when. Those cute lambs of early spring now look like adult sheep, but early in the month it may still be possible to distinguish them from their mothers because the ewes have been shorn and the lambs have not. Later you only seem to see one type of sheep per field - ewes or lambs - but it is often hard to tell which. Certainly some lambs have already gone to the abattoir, as evidenced by the occasional truck laded with them that passes you on rural roads. The breeding ewes will remain in the fields all winter.
You can still see herds of bullocks - presumably not long for this world - but strangely there also seems to be an upsurge in cows with calves this month - beef cattle, since dairy calves are separated from their mothers at birth. Dairy herds do not seem to be that common in the south east. In theory they should not go into barns until later in October, but how fast the grass is growing and how soft the ground is may be decisive factors.
Late September sees the beginnings of the deer rut, which climaxes in October. The reason for this timing is so that the young can be born in spring, when the weather is warming and the grass is starting to grow again. A wonderful place to observe the rut is Richmond Park in London, where dominant red deer males gather harems of females (or rather the females gather round the male – it is they who choose where to be) and mate with them, while chasing away challengers.
In late September all this tends to be at a fairly early stage, with the males roaring at each other (they build up their throat muscles over the summer so they can extend their larynx to produce deeper tones) and rubbing their antlers in the bracken to mark out territories. The females, meanwhile, wander around apparently unconcerned, but in places start to gather around the males. For more information on the red deer rut at its height, see the October deer rut page. For photos click here.
Red deer are not a wild species in southern England (though they can also be found on the Knepp Wildlands near Horsham), but fallow and sika deer rut at around the same time. The fallow deer rut seems to consist of a croaking competition between males (they sound a bit like oversized frogs...), with the females not necessarily making their choice clear in the same way that red deer females do. Knole Park in Kent is one possible place to see this and from Boughton Monchelsea church on the Yalding to Sutton Valence walk you have a grandstand view of another fallow deer park. They are also found in Hampton Court Home Park, Bushy Park and Richmond Park, though they tend to be rather inconspicuous (or hard to find) in the latter place.
If you are lucky enough to spot signs of fallow or sika deer rutting in the wild, keep your distance. The red deer in Richmond Park and Knole Park also need to be treated with respect, but are obviously more used to being watched by humans. Roe deer, the other native wild species, ruts in late July and early August, while the introduced muntjac deer mates year round.
More September pages:
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