Category: Science

I had a discussion recently with a former moth-er who disposed of her trap after having an ethical pang of conscience about all the moths she had been disturbing over the years. She suggested that there are hundreds of thousands of people trapping all over the country and that we’re interfering with reproduction cycles by doing so. I felt her opinion was at best misguided.

My immediate thought was that that number was way off. I know two other people in this village of 4000 or so who trap regularly, as do I, but this is quite a sciencey village, close to Cambridge, so could be exceptional. There’d have to be 3-4 people in every of the 44000 villages and towns across the UK for there to be hundreds of thousands of people trapping. This from a straw poll I conducted among moth-ers online is very unlikely. If anything there are a few hundred across the British Isles mothing regularly, maybe at most 1000. Even if we assumed 1 per 1000 households, there are just 28 million households, that would still only be 28000, but I reckon the hobby is done by far fewer people.

Gary G: I’m not a moth trapper, I joined to learn more about moths. From my experience collecting ladybirds using sweep nets and beating trays I often find they mate in my specimen tubes before I release them. I wonder if this happens in moth traps?

Alan S: Yes it does. Sounds like [mating in moths traps] might be a beneficial side effect then. Add to that the huge benefits gained for ecology from recording the moth distribution and population trends and I’d say you’re on to a winner.

Jerry S: Also, more male species seem to be attracted to light.

Alan S: In the grand scheme of things it doesn’t make much difference unless people are constantly trapping the honeypot sites for scarce species and even then as long as it’s catch and release it should be OK. We survey lots of sites and these don’t get done as regularly as we’d like. The sites are huge and we only cover a tiny fraction each time we survey so impact is negligible.

Shaun P: If trappers are doing the right thing and sending in records, it should be easy to find out the number. I’m in Cornwall and I suspect the number of regulars is quite low judging by records and talking to others.

Sean O: Cars are a bigger problem…a drive in the countryside at night, moths continually in the headlights with several hitting, then multiply that by the number of cars on the roads around the country…that’s a lot of moths in a year!

Giles K-S: My experience (in rural Herefordshire) is that I actually see very few moths in the headlights – so few that you can almost count them individually. I think it’s just a symptom of the wider decline in insect numbers.

Mark G: I hardly see any. I remember the moth snowstorms of old in the 1960s.

Sciencebase: Yes, been discussing this for a while, 15-20 years ago, driving anywhere meant cleaning the windscreen regularly, not so these days.

Giles K-S: Moth traps only attract moths passing within a very short distance of the trap – in the range of 3 to 10 metres. Of much greater concern is the large number of other artificial light sources disrupting the activity of moths, bats and other nocturnal species.

Mark S: There are certainly [fewer] than 150 trappers in VC55 Leics & Rutland, and I’m sure there are many VCs with many fewer. Responsible catch & release, and recording does far more good than damage.

Leonard C: Static traps run all the time all around the country and provide valuable data. The only way we can help decline is to actually record numbers and then act upon such data by increasing habitat and foodplants.

Summer de G: [Moth-trapping] probably has no more impact than leaving outside lights on all night or garden lights.

Ben S: Moths are at more danger from birds, the bat roost at the bottom of my garden, artificial lights at night, and our clearing land, driving our cars etc.

Derek C: [Simply] mowing the lawn probably [kills] quite a few!

Kiera C: I think moth people are likely to be far less of a problem than the broadcast application of pesticides by industrial agriculture, the destruction of habitat, and the effects of climate change. If trapping and freeing moths just gets people to think about those bigger issues, to join environmental groups, to change their patterns of consumption, and to see the beauty in nature so that they want to look after it and protect it, then that possibly outweighs harms.

Lee T-W: I find that numbers in my garden increase slightly year on year (for common species). I wonder if attracting them brings them together to create greater breeding opportunities, also trappers are likely to manage their mini-habitat more beneficially?

Pete M: As long as people are sensible with holding off if you’re attracting predators, do all you can to prevent casualties, don’t trap every single night, and always send records in so your data has some use, I can’t see any real ethical issues.

It’s always a delight to spot a big lep in the scientific trap when you approach it each morning. This morning’s treat was a Privet Hawk-moth (Sphinx ligustri), but once I’d lifted the lid I realised there were two. This is a big moth (55 mm from the nose to wing-tip, with startling pink and black markings on its body and hindwings, which are revealed when it opens its wings.

This is the largest resident moth species in the British Isles. It flies June to July in a single breeding season. I had previously seen and phone-photographed a pair roosting on a concrete bollard in the village (14 Jun 2019, 21h20, Wilkin Walk, Cottenham, to be precise). But, not seen any since.

In repose, the Privet Hawk-moth is, like many other species, well camouflaged against natural backgrounds, such as leaves and bark. Its startling colours when it opens its wings are presumably an anti-predator adaptation like those of many other species, but not latching on to the “eyes or face” type of the Eyed Hawk-moth or the Emperor Moth. Black and pink stripes are more likely to be perceived as venomous or otherwise poisoning, bad-tasting, or stinging.

A Peppered Moth, Biston betularia, was drawn to my scientific moth trap last night. This species is probably the most important moth, scientifically speaking. It’s something of a Victorian scientific hero, in fact, and a speckly example of how evolution doesn’t always need millions of years to happen, but can take place within a decade or so if not faster.

During the sooty days of the Mancunian branch of Britain’s Industrial Revolution, this creamy white moth with black peppery speckles evolved to an almost black form (Biston betularia betularia morpha carbonaria). Originally, the light form had been well camouflaged on lichen, which meant it was hard for birds to see and so safe from becoming avian lunch. But a lot of the lichen was killed off by the smoke and smog of the industrial revolution and coated with soot. Those mainly white Peppered Moths were no longer well camouflaged and were easy pickings for birds.

However, a mutation arose in this species that for all intents and purposes gave rise to a melanic, dark, form of the moth. No more bright white but a sooty black moth that was now camouflaged on the dark surfaces of the industrial era. Now, the dark moths that evaded detection by birds could live to breed and pass on their genes for this melanism. It seems that the mutation arose around 1819 as the carbonaria form was not noted by naturalists before this date.

The rapid change from a bright to a dark, melanic form, industrial melanism as it is now known, provided evidence of survival of the fittest, natural selection, and evolution in action. By the end of the century, 95 per cent of the Peppered Moths in Great Britain were carbonaria.

The melanic form began to decline in Britain after the Clean Air Act of 1956 when smokeless fuels came to the fore and uncapped pollution was no longer acceptable. I am yet to see the melanic form, hence the lack of photos, but it certainly still exists in the wild. This reversal of the adaptation lends additional support to the evidence for the original industrial evolution.

There was some concern in the 1990s that the original research proved nothing as it didn’t take into account the moth’s natural resting places and that moth migration might skew the actual results and may have led to some of the effect. However, interesting research by the late Michael Majerus discussed and followed-up here in the journal Biology Letters provides strong evidence that reinvigorates the original hypothesis of industrial melanism in the context of predation by birds.

The authors talk of how “caveats about the predation experiments discussed in Majerus’s book, critiques by other biologists, as well as points made particularly forcefully in a review of the Majerus book, were soon exploited by non-scientists to promote an anti-evolution agenda and to denigrate the predation explanation”. They add that “both the public in general and even evolutionary biologists began to doubt the bird predation story.”

Their paper also debunks the creationist ideas that arose when doubt was first cast on the idea of this rapid evolution of an animal as its surroundings changed through industrialisation and into the post-industrial world of the North of England. Moreover, industrial melanism is seen in other types of moth and provides parallel evidence for the changes observed in the industrial evolution of the Peppered Moth.

UPDATE: 25 Jun 2019 – Another Poplar turned up overnight along with two Privets, an Eyed, six Elephants, and a Small Elephant! And 150 other miscellaneous specimens.

My first taste of mothing proper was in a friend’s garden, where I turned up at about 8am the night after he’d “lit up” his 40W actinic, homemade, collapsable Robinson trap. I mentioned it on the blog at the time, you may recall – The Nouveau Mottephile. Regular readers will have noticed I’ve blogged about moths quite a lot since that fateful July morning. Anyway, on that morning I was startled by to be introduced to the diversity of the Lepidoptera, there were a few dozen moths in my friend’s trap, almost all of which I had never seen before. I only had a phone with me so, the photos I got were of poor quality. One of the most startling and beautiful moths in the trap is the subject of this post, the Poplar Hawk-moth (Laothoe populi).

The description on the UK Moths website about the Poplar Hawk-moth reads as follows:

“Probably the commonest of our hawk-moths, it has a strange attitude when at rest, with the hindwings held forward of the forewings, and the abdomen curved upwards at the rear. If disturbed it can flash the hindwings, which have a contrasting rufous patch, normally hidden.”

This specimen was in the trap this morning, the same trap, which I bought from my friend in the autumn of last year, having become hooked on mothing. It’s the first time I’ve seen this species since July 2018. I photographed it but obviously didn’t irritate it at all as it never flashed its underwings.

Other Hawk-moths that have featured on the blog:

Lime Hawk-moth, Mimas tiliae

Elephant Hawk-moth, Deilephila elpenor

Eyed Hawk-moth, Privet Hawk-moth, Small Elephant, Pine Hawk-moth, and Hummingbird Hawk-moth are in my Mothematics gallery.

As of 10 May 2022 yet to see or photograph: Death’s Head, White-lined, Convolvulus, Oleander, Willowherb, Spurge, Bedstraw, Striped, Silver-striped, Broad-bordered Bee, and Narrow-bordered Bee Hawk-moth.

After much anticipation, Peter Marren’s new book – Emperors, Admirals & Chimney Sweepers (The weird and wonderful names of butterflies and moths) recently landed on my desk for review. One of the things I find most fascinating about the lepidoptera is their nomenclature, both the common names – such as Angle Shades, Lime-speck Pug, and Red Admiral, but also the scientific binomials including Aglais io, Autographa gamma, and Polygonia c-album.

Indeed, so fascinated was I that I put together a book proposal to write about how the butterflies and moths all got their names…but Marren had already beaten me to it and has done a far better job in writing about them than I ever could.

He explains the origins of almost every species you’re likely to come across in the UK. He tells us why the pug moths are called pugs (yes, it is to do with their resemblance in some characteristics to the flat-faced dogs). He explains that The Sprawler moth has a “star-gazing” caterpillar names after the Italian astronomer, Cassini. There’s also proof as to why the Common Wainscot is so named and it is indeed for the plain wooden panelling, as Mrs Sciencebase suspected when I presented that very moth in a pot a few days ago!

The infamous Death’s Head Hawk-moth, once a harbinger of doom, is in there as is the Jersey Tiger, the Emperor, and the Brimstone (both butterfly and moth). There are plenty of carpets too…which was never an insult as back in the day when these leps were named, having a carpet was a luxury, naming a patterned animal that recalls an elaborate carpet was therefore a compliment.

An excellent book for moth-ers and butterfly enthusiasts in the Little Toller Field Guide series. Highly detailed index makes it easy to look up the latest species that appears in one’s trap or is spotted in the garden our elsewhere – Cinnabar, White Ermine, Light Brocade, Garden Pebble, Waved Umber, Mottled Rustic and so on. There are well over 2500 species of lepidoptera in the UK and a few migrants and vagrants. Keep up to date with my own personal sightings and their names in my Mothematical Gallery.

Incidentally, there was a rumour that the proper name of the Red Admiral butterfly, Vanessa atalanta, is the Red Admirable. Even novelist and lepidopterist Nabokov insisted on this point. Marren discusses the etymology and in an update for the paperback, suggests that both words were probably in use very early.