A moth-recording group · Purbeck, Dorset
There’s a light
on the heath tonight
Tonight · lamp on at dusk
Every night from March to November a lamp burns on Sallow Heath, and whatever flies to it, we write down.
We are a small group of volunteers with a mercury-vapour lamp, a white sheet, a Robinson trap and a lot of egg boxes. We set them out on the sandy track at dusk, stay while it is busy, and come back at first light to count what stayed.
The moths are not drawn to the lamp the way you and I are drawn to a lit window. In 2024 researchers filmed insects around lights in flight: they turn their backs toward the brightest thing they can see, which is how they keep level under an open sky. Beside a lamp that rule traps them in orbit.
So we go gently. Every moth is named, counted and let go into the long heather, and the records go to the county moth recorder, where they join the national picture.
Emperor
Moth
The only British silkmoth,
at home on the heather
In April and May the males fly in sunshine, fast and low over the heather, following the scent of a female that has not yet moved from where she hatched. On the right spring morning one lures a dozen.
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Elephant
Hawk-moth
Pink as a willowherb flower,
named for its caterpillar
The caterpillar can pull its head back into its body like a trunk and swell four false eyes. The moth it becomes hovers at honeysuckle at dusk, and on a June night it is the one everyone wants to hold.
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Merveille
du Jour
Lichen on oak bark,
the turn of the year
From mid-September to late October it arrives from the oaks at the edge of the heath, green and black and white, and vanishes the moment it lands on bark. The first one of the autumn is always passed round.
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A night in July, as logged
One night at the trap
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01 · Sunset
The trap goes out
A Robinson trap and a white sheet go out on the sandy track, with a 125-watt mercury-vapour lamp and the generator well down the slope, out of earshot.
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02 · Dusk
Lamp on
The first moths come before it is fully dark: a Large Yellow Underwing, a True Lover’s Knot from the heather, a Burnished Brass that flashes in the torch beam.
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03 · Midnight
The busiest hour
Warm, overcast, no moon: the nights moths like best. The sheet is crowded, pots are passed along the line, and someone is always saying “look at this one.”
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04 · First light
Lamp off
The moths that came to the trap have settled in the egg boxes inside it. We switch off before the robins are up; they learn where traps are.
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05 · The count
Every moth named
386 moths of 91 species. The list goes to the county moth recorder; the moths go into the long heather, out of sight of the birds.
Plates I – XII
Twelve moths, four hundred nights.
Warning colours,honestly meant Buff-tip
A snappedbirch twig Large Emerald
A green thatfades in days Peppered Moth
Salt and pepper,and a black form The Sallow
The colour ofturning leaves
Try it yourself
Open
the trap
At first light the trap is full of egg boxes, and in the egg boxes are the moths. Lift them one by one, name what you find, keep the tally, and let them go.
Do the morning check
Come along
The next
nights
Moths like warm, still, cloudy nights, and they come best when the moon is small. Times below are worked out for the heath: the lamp goes on half an hour after sunset.