Moth Report 2019 by Harry Rutherford

I’m now in my fourth year of running a moth trap in the garden, and I am still catching new Species frequently. I’ve had 46 new species this year, taking my garden list to 525 in total. And there are still plenty of relatively common species I haven’t had.

When I tell people how many species have occurred in the garden, they tend to be encouraged by it, as evidence of a healthy local insect population. I'm not so optimistic. Insect numbers are in decline in the UK and around the world, and the number of specie isn't the same as the number of moths; the abundance can decline dramaticall without any species disappearing completely. Driving through the countryside at night used to leave you with a moth-splattered windshield; it doesn’t anymore.

If you want to help insects, grow native plants. Species like laurel and rhododendron support no native insects at all, while rowan supports 28 species, hazel 73, hawthorn 149, and oak trees can support a remarkable  284 insect species, plus 324 species of lichen. The same applies to flowers; there is a lot of emphasis placed on growing plants which provide nectar and pollen for insects, but if you choose native species you also provide food for caterpillars. The achillea in our garden supports at least three species of moth on its own. The new wildflower planting around the bowling green in Dulwich Park has already attracted two day-flying longhorn moths which feed on scabious, including the very local Nemophora cupriacella.

I caught several species I had admired in the field guides, including Waved Black, Birch Mocha and Swallow Prominent. Perhaps the most glamorous was Leopard Moth, a large white moth with slightly metallic blue-black spots, whose caterpillars live for two or three years inside the wood of tree branches. Another particularly attractive one is Scarce Silver-lines, which is bright green with thin white diagonal lines running across the wings, although my specimen was unfortunately a little worn.

Perhaps the weirdest species I found in the garden was Luffia lapidella, one of the bagworms. They are called that because the caterpillars live in cases made by sticking together bits of Plant material, like terrestrial versions of caddisflies. The females are wingless, which is not unusual in moths: they just stay where they are, release pheromones, and wait for the males to come to them. But in the case of Luffia lapidella, in the UK they are also parthenogenetic; i.e. they reproduce via virgin birth, and the males are completely absent. The larvae feed on lichen, although they are easy to miss because they are 6mm long and their lichen-covered cases make them extremely well-camouflaged.

There were also a few rarities. There was an influx this year of the rare migrant Scarce Light Plume, with records across southern England. My one was probably the first for Surrey (natural history records still use the historic county boundaries, so Dulwich is still in Surrey for moth purposes).

The most surprising record was one which unfortunately has to remain unconfirmed. In August I found a caterpillar feeding on verbascum which appeared to be either Wate Betony, which is an extremely rare immigrant species with only a couple of confirmed records in Dorset since the nineteenth century, or Striped Lychnis, a very local species with the nearest population in the Chilterns. To confirm the ID I would need to rear it to an adult, and even then it would need to be dissected to confirm the species. I did try to do this, but unfortunately, /the soil I gave it to pupate in was too damp and it went mouldy. It seems unlikely that either species has established a previously undetected population in South London—perhaps it was a single wandering female—but I will be checking for the caterpillars again next year.

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