The second wave: which British species are still to fly

Britain has one ant that flies loudly and about fifty that don't.

Lasius niger, the black garden ant, is so abundant and so synchronised that its flights account for nearly everything the public sees and almost everything the press reports. In the RSB's national survey it made up the large majority of the ants people sent in. Its main run is early July to about mid August, so it isn't quite finished as you read this, but the big synchronised swarms are behind us and it genuinely feels like the end.

What's actually happened is that one species is winding down. The rest of the list is still working through August, and several of them haven't started.

There's a physical reason the second half of the season looks different, and the careful version of it is nearly fifty years old.

Boomsma and Leusink spent three summers on a Dutch island recording the weather at the moment queens took off, for Lasius niger, L. flavus, Myrmica rubra and M. scabrinodis. You would expect each species to have its own temperature. They found the opposite: no significant difference between the four in mean air temperature at flight. All of them went up somewhere in the high teens to low twenties Celsius, roughly 15.9 to 23.8 °C (60.6 to 74.8 °F) for niger and 17.3 to 22.7 °C (63.1 to 72.9 °F) for M. rubra, windows that overlap almost completely.

The difference showed up in the light. Global radiation, in joules per square centimetre per hour, ran from 133.6 upwards at L. niger flights but from as little as 31.3 at Myrmica flights, a floor roughly four times lower. That tracks queen weight almost exactly: a niger queen is around 25 mg, a flavus queen 18 mg, a Myrmica queen 4 mg. A heavy queen sits in the open soaking up sun before takeoff, and the bare sand of a niger colony's habitat hit 41 °C (106 °F) at flight times, against 22 °C (72 °F) in the damp grass tussocks where Myrmica live. A 4 mg queen has far less body to haul into the air and can do it without the solar top-up.

The constraint on the later species is looser, then, rather than colder. They can use a grey, ordinary late-August afternoon, and they do, in short local bursts that never add up to anything you would call a swarm.

One more thing from that study is worth carrying into August. Before 20 August, none of the four species flew in wind above 1.7 m/s, which is under 4 mph. After 20 August, all of them did, up to 2.5 m/s and in niger's case 3.4 m/s, nearer 8 mph. The season's last flights happen on days that would have been vetoed a fortnight earlier, which is either an urgency effect or a run-out-of-options effect, and the paper doesn't claim to know which.

These are the ants that made you swear when you knelt on the lawn.

Myrmica rubra and its relatives are the small reddish ants with a real sting, and between them they cover the rest of the summer. M. ruginodis has alates sitting in the nest from early July and flies mostly in August. M. rubra itself runs August into September. M. scabrinodis is recorded from July right through to September, and M. sabuleti from August into early September.

The flights are small enough that you can stand next to one without registering it. Look for a few dozen winged ants coming off a single nest entrance in the grass rather than a column over a chimney. Don't assume afternoon either: on the Dutch data M. rubra went up between 9am and midday or between 5pm and 8pm, and M. scabrinodis at any point across an eight-hour span.

M. scabrinodis is the genuine awkward case. In that same study it was the one species showing no defined preference in daytime, radiation or humidity, and its local flights happened in much warmer, drier conditions than its big ones. That is an inconvenient result if you are trying to forecast it, and an honest one to report.

If you keep ants, this is the bit of August to pay attention to.

Lasius umbratus, L. mixtus and L. sabularum are yellowish, mostly subterranean, and socially parasitic. Their queens cannot found a colony alone. After mating, a queen has to get into an established nest of a host species, displace the resident queen, and be adopted by workers that are not hers. L. umbratus goes after L. niger, L. platythorax or L. brunneus; L. mixtus chiefly after L. flavus. What results is her brood raised by someone else's workforce, until the host workers die off over the following year and only her own are left.

The gaining-entry problem has produced one of the stranger things you can see on a British lawn. L. umbratus queens have been recorded wandering over the surface of a L. niger nest carrying a dead niger worker, apparently as a chemical passport before attempting adoption.

Timing runs later than most people expect. L. umbratus flies from mid August to late September. L. mixtus is August and September. L. sabularum has the longest window of any British ant here, July right through to October, and its alates sometimes overwinter and fly the following May instead.

The queens are large and gingery and turn up on paving in late summer looking like something you don't recognise. If you catch one and put her in a test tube on her own, nothing will happen. There's nothing wrong with her; she's missing the host workers the whole strategy depends on, which makes her a considerably more involved project than a niger queen in a tube. Plenty of people find that out the slow way.

Solenopsis fugax is tiny, yellow and almost entirely subterranean, and it makes a living by robbery. Its nests sit right up against colonies of much larger ants, Lasius and Formica mostly, connected by tunnels deliberately too narrow for the host workers to squeeze through. The thieves go down them, take brood, and cannot be followed.

Winged ants are in the nest through August, but the flights themselves come later than the rest of this list, on warm afternoons in September and October. The alates are small and pale enough to be written off as midges.

Lasius flavus, the yellow meadow ant out of old lawns and grassland, flies late July and August and gets its own post shortly. Lasius alienus is July to September. Formica fusca has winged queens and males in July and August, though it barely swarms at all: they leave the nest in dribs and drabs and mate on the ground, which is why nobody notices. The pavement ant Tetramorium caespitum is finished or nearly so, since its British flights run late June to early August.

Lasius fuliginosus, the shiny jet black ant that runs long trails along hedge banks, deserves its own line for sheer cheek. It is a parasite of a parasite. Its queens found colonies inside nests of the umbratus group, which had themselves been founded inside somebody else's nest. You occasionally find a mixed nest with black fuliginosus workers and their yellow or brown hosts still running around together.

Latest of all is Stenamma debile, whose alates are most often collected in late September or October. It lives in undisturbed leaf litter in deciduous woodland, its colonies rarely exceed a hundred workers, and the workers are small, slow and pin-point eyed. Almost nobody has watched it fly.

The practical difference between July and August is how you look.

In July you look up, because the flight is above head height and there are thousands of them. From here on you look down, and at specific places: rough grass and old lawns for flavus and Myrmica, paving and paths for a big gingery parasitic queen from mid August, undisturbed woodland leaf litter if you want Stenamma in October. A queen on the ground after an August flight is often a fraction of the size of the July ones, so the search image has to change with the month.

The dates above are recorded flight periods, not a fixture list, and they come from British recording rather than from anywhere warmer. Local weather still decides the day. That was true in July and it's more true now, because the later species are less synchronised and, on the evidence above, much less fussy about how bright it is.

That's what Dealate does with them: scores the days ahead for the species that are actually in season where you are, hour by hour, so an August evening that's worth going outside for doesn't look identical to one that isn't. A reason to look up, not a guarantee.

If you want the mechanics first, what is a nuptial flight covers the event itself, the flight timetable covers which hour to be out, and how to find a queen ant after a flight covers the ground search. If you've already got one, you caught a queen, now what is the next few days.

British flight periods, hosts and habits are from the species accounts of the Bees, Wasps and Ants Recording Society, which is the national recording scheme for British ants. The weather measurements, the queen weights and the radiation figures are from Boomsma & Leusink (1981), Weather conditions during nuptial flights of four European ant species, Oecologia 50: 236 to 241, whose observations were made in the Netherlands between 25 July and 1 September. The abundance figure for the UK season is from the Royal Society of Biology's Flying Ant Survey, analysed in Hart et al. The papers behind the model are set out on the methodology page.