Introducing Common Migrant Moths (part 2) - the next eight

Small Mottled Willow (above) has probably been Britain's most ubiquitous migrant moth this year. The arrival of 19 more in my trap over the past couple of days has prompted me to post the second part of this blog on our common migrant species. 

Part 1 (link here) looked at the seven commonest immigrants - the ones that UK moth recorders are most likely to encounter. The present post considers the next group of eight species that sit in that 'grey zone' between rare and common, although what that means in practice will depend on where you are trapping. Moth recorders on Britain's south and east coasts will generally get better numbers than those inland, but even down here in Dorset I am very happy when any of these species turn up.

The eight moths covered in this post all had 3,000+ British and Irish records between 2010 and 2019, taken from the Atropos website. This is compiled by Sean Clancy, who does a great (and unenviable) job keeping on top of the data using information from county moth recorders. Obviously, these numbers will now be out of date - this year's Small Mottled Willow influx may well move that species into the 'very common' bracket - but they still give useful pointers towards what's common and what's not.

[Note - this blog was updated on 26 July 2026 with additional text and images.]

Top of this group of eight is the Vestal (below), with 15,405 records from 2010 to 2019.

Vestal Rhodometra sacraria - Dorset 22.9.19

This is a lovely moth. Linnaeus named it sacraria (from 'holy' or 'sacred') either because its colours reminded him of priestly robes or its simple yet beautiful pattern suggested virtue or chastity. The early collectors who named it the Vestal were clearly thinking of the latter, which is both odd and yet typical of the whimsical nature of our common moth names. (Maintaining a chaste and virtuous existence will of course be the last thing on a moth's mind.)

Identification is straightforward. While the colours can vary (see below), the basic pattern never changes. When resting, the moth has an upright, tent-like posture that differs from many of the other members of its family (the Geometridae) that spread their wings flat or hold them together vertically.

Globally, the Vestal is a widespread species, occurring in Europe, Asia, Africa and South America. Early arrivals can breed in Britain, with 'home grown' second generation individuals adding to summer and autumn migrants. But there is little evidence of that they can successfully overwinter here. 

An interesting feature of the Vestal is that its colour depends on the temperature experienced by the growing caterpillar. The 'classic' look of a strong pink stripe across a light straw-coloured background (as in the above photo) suggests that the caterpillar lived through high temperatures, so this moth was probably an arrival from southern Europe. Duller colours indicate that its origin may have been further north. The darker example pictured below, an autumn arrival, may well have bred in England.

Vestal Rhodometra sacraria (darker example) - Dorset 27.10.22

Britain's migrant moth of the moment, the Small Mottled Willow, comes second on the list with 8,248 records 2010-2019, but the annual average is now surely higher. This species is well known for its irregular habits - it's either feast or famine, with large numbers arriving in some years while other years see hardly any. I trapped only 13 last year (2025), while my 2026 total to date is 228! 

Small Mottled Willow Spodoptera exigua - Dorset 12.6.25

At first sight, Small Mottled Willow is a rather non-descript member of the noctuid family. However, despite a wide variation in size (which we have certainly seen this year), they are easy to identify once you get your eye in. The pinky-orange oval and kidney mark are good clues, but it is the moth's posture that is the real give-away. When at rest, its wings are held in a similarly tent-like manner to the Vestal, and often partly rolled under the body, giving a generally narrow appearance. Pale Mottled Willow is perhaps the most likely confusion species, but that has wider wings that are held flat when at rest. 

Known also as Beet Armyworm, Small Mottled Willow is found from North America to Australia, and causes significant damage to crops in tropical and semi-tropical lands. Its capacity to trouble farmers in Britain is severely limited by its inability to survive the colder winters here. For the time being.

Third on our list is Scarce Bordered Straw, with 7,071 records 2010-2019. Given that this moth is more likely to be seen here than its close namesake the Bordered Straw (see later), its name is rather unhelpful - which applies to a number of other British moths, as it happens.

Scarce Bordered Straw Helicoverpa armigera - Dorset 1.9.24

Scare Bordered Straw is one of the more tricky moths to identify because it lacks any one obvious distinguishing feature. The fact that it's a variable species doesn't help. At first sight, it is a classic member of the noctuid family (see my blog on moth family ID here), with a chunky, rather thickset appearance and a flat resting position. Consistent features are the oval and kidney marks which have fine dark outlines and central spots. Also look out for the wavy black cross-lines and the dark outer band (at the bottom of my photos). Here is a more red-brown coloured individual:

Scarce Bordered Straw Helicoverpa armigera (reddish-brown colour) - Dorset 27.10.22 

Also called Old World Bollworm, Scarce Bordered Straw is a major agricultural pest in tropical and subtropical regions of Africa, Asia and Australia, as well as being found across much of Europe. Its caterpillars are however rarely seen in Britain.

Sticking with the noctuid family, our fourth species is the Pearly Underwing (below), with 5,663 records 2010-2019. Known also as the Variegated Cutworm, it is found in North and South America and East Asia as well as Southern Europe. As with the previous two species, Pearly Underwing is an agricultural pest in warmer climates.

Pearly Underwing Peridroma saucia - Dorset 17.6.26

Like Scarce Bordered Straw, Pearly Underwing seems at first glance to be a rather undistinguished moth. But although its pattern and colouration are variable, there are several distinctive features. First, it is a large moth, its size range overlapping with that of the familiar Large Yellow Underwing. Second, as the name suggests, its hindwings have a pearl-like translucence, although this is set against dark veins and a dark band around the edge - and getting the moth to show you can be a bit of a challenge. Don't expect to see a shining white hindwing. But the best identification character of all requires you to look at the moth from the side, which reveals a narrow ridge of scales like a Mohican haircut - strictly, the thoracic crest (below).

Pearly Underwing Peridroma saucia (side view) - Dorset 17.6.26

While three of the commonest immigrant moths to Britain are classed as micro-moths (see my previous migrant moth blog), only one of the present group of eight falls within that category. It's one of my favourite species - the Olive-tree Pearl Palpita vitrealis (below), after which this wildlife blog was named. There were 5,065 records of this species between 2010 and 2019.

Olive-tree Pearl Palpita vitrealis -Dorset 10.8.20

Identification is straightforward, as the combination of plain, translucent white wings with a brown leading edge (costa) appears in no other British moth species. While the wings of the Box-tree Moth Cydalima perspectalis are translucent, they usually have thick black edges - and the moth is much larger.

Olive-tree Pearl is a member of the crambid family, many of which seem to have a yearning to travel long distances; these include two very common migrants (Rusty-dot Pearl Udea ferrugalis and Rush Veneer Nomophila noctuella) featured in my previous blog and a number of much rarer arrivals to our shores. Primarily an old world species, Olive-tree Pearl is found in Europe, Africa and Asia: I have recorded it in India (Goa), where it was a nice surprise to see a familiar moth in such exotic surroundings.

Despite its name, the caterpillars of Olive-tree Pearl feed on a variety of species including Ash, privets, forsythias, Strawberry Tree and Summer Jasmine as well as Olive. To date, there are no records of it having successfully bred in Britain, although egg-laying has been observed. Once again, the moth cannot successfully over-winter here.

Heading back into the world of macro-moths, our sixth species is Bordered Straw (below), with 3,789 records between 2010 and 2019.

Bordered Straw Heliothis peltigera - Dorset 21.9.20

Bordered Straw is a helpfully distinctive moth. Despite some variation in its background colour (see below), the overall pattern of markings is generally consistent: a dark kidney mark contrasting with a lighter and plain background. Compared with Scarce Bordered Straw Bordered Straw looks 'cleaner', especially in its lighter forms. Note that there is an further confusion species - Eastern Bordered Straw: see the update added at the end of this blog post.

Predominantly an old world species, the range of Bordered Straw is centred on Southern Europe, North Africa and West Asia. Unlike the other moths described in this blog post, it is sometimes seen flying during the day searching for flowers. I spotted a day-flier on Grange Heath, Dorset last month (below), showing the dark band on its hindwing which is usually hidden when the moth is at rest.

Bordered Straw Heliothis peltigera - day flying at Grange Heath, Dorset 22.5.26

Like the Vestal, as already described, the background colour of Bordered Straw is affected by the temperature experienced at the larval (caterpillar) stage, with lighter individuals likely to have bred in warmer climates. Early arrivals to our shores can breed here, giving rise to a second generation that can appear darker than the first arrivals: compare the September individual above with one from in June (below) which was almost certainly a migrant arrival. However, the moth is unable to over-winter here.

Bordered Straw Heliothis peltigera - Dorset 25.6.25

Coming in at number seven, the Convolvulus Hawk-moth (below) is one of the largest moths found in Britain. It is of a similar size to the resident Privet Hawk-moth and only beaten by the massive Death's-head Hawk-moth, an extremely rare migrant species that has yet to find my garden (but I live in hope). There were 3,475 records of Convolvulus Hawk-moth between 2010 and 2019.  

Convolvulus Hawk-moth Agrius convolvuli - Dorset 6.9.16

While the plain and streaky wings of Convolvulus Hawk-moth are similar to those of Pine Hawk-moth, the size difference easily separates the two species - the wing length of Pine Hawk-moth rarely exceeds 40 mm while Convolvulus can reach 55 mm. That is in the size range of Privet Hawk-moth, which also has pink stripes on its abdomen. However, Privet Hawk-moth has a distinctly black thorax (not grey) as well as dark-brown forewings and (if visible) two black bands on the hindwings, all features that are missing from Convolvulus Hawk-moth.

In Britain, Convolvulus Hawk-moths tend to arrive late in the season with numbers peaking in September. Adults are particularly attracted by the nectar of tobacco plants (Nicotiana) and can be observed feeding on flowers at dusk. Some moth enthusiasts have this plant in their gardens for that purpose; I'm afraid that I don't, but I still manage to see a few Convolvulus Hawk-moths here in Dorset each year. 

Like the previous two species, Convolvulus Hawk-moth is restricted to the old world, and is distributed widely across Africa, Asia, Australia and Southern Europe - although most European records appear to relate to individuals that have travelled from Africa. Those arriving in Britain may well mainly be the offspring of these first generation migrants, hence the late arrival times. While the moth's larval foodplants (bindweeds, as the name would suggest) are frequent in Britain (especially in my garden), the climate appears too severe to allow it to over-winter here. 

 

Convolvulus Hawk-moth Agrius convolvuli giving a me sharp stare - Dorset 26.9.24

Which brings us to the last species in this brief survey - the Gem (below). Although this geometrid just meets my 3,000+ criterion (the 2010-2019 figure being 3,038 records), it has (for me) been the the most elusive of this group of migrants. It wasn't until 2024 that I finally saw one and, to date, I've only had two more records here (both in 2025). I have no idea why this species doesn't seem to favour my trap, and I'm trying not to take it personally.  

 

Gem Nycterosea obstipata (male) - Dorset 2.5.25

The Gem is not a very conspicuous moth, being slightly smaller than Garden Carpet. Unusually for a moth, the male and females have different wing markings (sexual dimorphism, in the jargon). The females have dark wings, with a distinct black dot edged with white - presumably the 'gem' of the common name. (All of my Gem captures have been males, so I don't have a picture of the female. However, there's a good image on the UK Moths website here.) Males have a lighter brown or orange-brown wings, with many cross-lines. While there is also a black dot, this usually lacks the white ring, although a lighter circle is visible in my image above. 

Primarily a European species, the Gem is another migrant that can breed, but not overwinter, in Britain. In Dorset, it can occur at any time between April and December; my three records were in April, August and November. While most moth migrants to our shores are more common in the south and east, the Gem seem to particularly favour these areas and has tended not to venture north of Yorkshire and Furness - or over into Ireland for that matter. Having said that, its British distribution increased significantly between 1990 and 2016 (Randle et al, 2019), so this migrant may become a more familiar sight in northern latitudes. And, I hope, in my Dorset moth trap. 

Right - this 'gang of eight' concludes my brief survey of Britain's most common migrant moths. As will be seen from the Atropos website mentioned above - or indeed any good field guide - very many more moth species reach our shores, but most arrive in much smaller numbers (sometimes only single figures). While I have been lucky to see a number of real rarities (perhaps the subject of a future blog), many more migrants have eluded my trap, which is both a matter of frustration (especially when other Dorset moth recorders have been more successful - you know who you are!) but also a useful incentive to go on searching. But be warned - hunting for migrant moths can become a bit of an obsession ...

Update - 26 July 2026. 

When I first wrote this post I omitted mention of an additional confusion species - the Eastern Bordered Straw Heliothis nubifera. This is because, first, it has been classed as extremely rare migrant to Britain and Ireland (only 39 records up to 2024 according to the Atropos website) and, second, I had never seen one so didn't have a photo to use. However, 2026 has been an extremely good year for Eastern Bordered Straw arrivals on our shores: I'm not sure what the current total is, but it must be well over 100 records. One finally turned up in my trap yesterday morning, so this is what it looks like:

Eastern Bordered Straw Heliothis nubifera - Dorset 24.7.26

While the kidney mark is similar in colour and shape to that of Bordered Straw, the rest of the forewing area is generally more richly marked, with brown blotches, better defined cross-lines and several black dots on the leading edge (costa).

As it happened, singles of both Bordered Straw and Scare Bordered Straw were also in trap, so I was able to picture all three together (below) - an uncommon sight for British moth recorders. 

Left to right: Scarce Bordered Straw, Eastern Border Straw and Bordered Straw - Dorset 24.7.26

References

Emmet, A. Maitland (1991) The Scientific Names of the British Lepidoptera: their history and meaning. Harley Publications.

Parsons, M. and Clancy, S. (2023) A Guide to the Pyralid and Crambid Moths of Britain and Ireland. Atropos Publishing.

Randle, Z. et al. (2019) Atlas of Britain and Ireland's Larger Moths. Pisces Publications.

See also the field guides and websites listed in a separate blog post (notably Waring & Townsend and the Dorset Moths website).

Atropos migrant moth totals are here.

Global range data is from GBIF.

Text and images (c) Mike Hetherington

Introducing Common Migrant Moths (part 1) - the Big Seven

It has been a slow start to the year for moth recording, but everything changed last night (22 May 2026) with the arrival of warm air from the south (likely from North Africa). Such conditions are ideal for finding migrant moths down here on the Dorset coast, and I approached the trap this morning with some anticipation. As well as bleary eyes: I was up at 4.20am, arriving only just before our local Robins and House Sparrows.

The final trap tally was almost 200 moths from 69 species. Seven of these species were migrants. Moth migration is a particular interest, and this morning's arrival gives me the perfect opportunity to look at the subject in a bit more detail. In this (and the next) post I'm reviewing the common migrant species that we get in the UK, several of which turned up here this morning. 

There's much to say about moth migration, but I'll keep it short for the present post. In summary, we are talking about those moth species that arrive, but do not generally overwinter, in the UK. While early arrivals may breed successfully, their offspring are unlikely to survive the winter months. As such, they are unable to establish permanent breeding populations. For the time-being. 

This caveat is important. Over the last 20-30 years, the British Isles have seen the arrival and establishment of several moth species (such as Jersey Tiger) who's status has changed from migrant to resident breeder. Indeed, British populations of many longer established species (like Large Yellow Underwing and Angle Shades) are regularly augmented by arrivals from continental Europe or further afield. In such cases it is impossible to tell for certain whether the moth in your trap has experienced a cross-Channel journey or just flown in from a local population, although weather conditions along with the presence of known immigrant species alongside them can provide useful hints.

So - which species are the known migrants? For a newcomer this is a bit baffling, but there is help at hand. The status of British moths is explained in the better field guides (see my blog post reviewing identification resources), and migrant species are considered in some depth by the Atropos journal and website. Atropos runs a 'flight arrivals' page where recorders can post details of new sightings, although I don't post on this as often as I probably should. For users of Facebook, Steve Nash runs the Migrant Lepidoptera (GB & Ireland) group, which carries news and images of migrant arrivals. There is a similar account on BlueSky.

OK - let's have a look at the common migrant species. These are spread across several moth families, suggesting that the tendency to migrate is either an innate Lepidopteran characteristic or has evolved separately many times. Now is not the time to speculate! Certainly, some families seem to be disproportionately represented in the migrant lists - notably the Crambid micro-moths as we will see. This and the next blog do not take a taxonomic approach. Instead, they focus on abundance, describing the migrant species that you are most likely to encounter. 

This blog post starts with what I'm calling the 'big seven' - the species that are so common that absolute numbers simply cannot be obtained. Some arrive in massive influxes: for example around 3 million Silver Y moths were recorded per hour on Shetland in 1996 (quoted in Randle et al., 2019). But please note that these are only 'big' in the sense of numbers. As we'll see, one species is very small indeed.

So let's begin with the Silver Y moth (pictured below and at the start of this post). This is found across continental Europe. Flying during the day as well as night, it is a fairly conspicuous species. Look for it nectaring on flowers during a sunny afternoon - as well as in the moth trap.

Silver Y Autographa gamma - Dorset 17.5.25

It's clear how Silver Y got its name. The combined shape and colour of the obvious Y-shaped mark are usually diagnostic, but bear in mind that there are a number of moths with a similar form and resting position that could cause confusion. Several are very rare migrant species (not covered in this post), but there are two common residents that need to be ruled out - Plain Golden Y and Beautiful Golden Y (below). In both cases the Y mark is usually split and lacks the silver sheen.

Non-migrant confusion species 1 - Plain Golden Y Autographa jota - Dorset 23.6.20

Non-migrant confusion Species 2 - Beautiful Golden Y Autographa pulchrina - Dorset 15.6.18 

Silver Y is a true migrant, in that the offspring of moths that have bred in Britain have been recorded undertaking a return migration to the continent in search of warmer winters (Chapman et al., 2002). While numbers in Britain have declined, its range has increased (a curious pattern found in some other moth species). Like several other moth migrants, Silver Y is arriving here earlier in the year as climate patterns change.

The second common migrant moth is even more conspicuous - the Hummingbird Hawk-moth (below). This is largely day-flying, although a few do turn up in moth traps. It is a real crowd-pleaser, buzzing around flowering plants and bushes in a distinctly hummingbird-like manner. Getting a photo can be a real challenge: they never seem to keep still.

Hummingbird Hawk-moth Macroglossum stellatarum in action - Dorset 12.6.15

Identification is straightforward: Hummingbird Hawk-moths are unlike any of our common hawk-moths and the combination of white, black, grey and orange colours - plus the distinctive flight pattern - is diagnostic. The distribution of this species within Britain has increased markedly over the last 45 years and there is recent evidence of adults being able to successfully overwinter here. This year, one was seen as early as February here in Dorset. Globally, the range of the species stretches from continental Europe right across to East Asia.

The next two common migrant species are both members of the same family as the Silver Y (the Noctuids), but lack its particular profile and markings: they stand out less from the many other species in that large family. Nevertheless, both have distinctive characters that enable easy identification.

Unlike many migrant moths, Dark Sword-grass (below) has shown a major decrease in numbers since the 1970s. Nevertheless, it is still recorded across much of Britain, although it remains unclear whether the species has successfully overwintered here. Last year it was the first migrant moth to turn up in my Dorset trap - on 21 February 2025, which seems unusually early for a cross-Channel arrival. But you never know. Globally. the species is widespread, occurring in South America, southern Africa and Australia as well as Europe, Asia and North America where it is most commonly found.

Dark Sword-grass Agrotis ipsilon - Dorset 16.3.23

Superficially, Dark Sword-grass looks like many other large noctuid species, but it has a particular diagnostic feature enabling easy recognition - a narrow black triangle ('dart') protrudes from the kidney mark (facing down in the above photo), with two more black darts pointing towards it from the end of the wing. See the enlarged image below:

Dark Sword-grass - detail of wing marking

The last noctuid in this list - the Delicate (below)- has a distinctly southern and eastern distribution in Britain. It is rare in Scotland and North Wales.

Delicate Mythimna vitellina - Dorset 7.6.17

The light (delicate?) tracery of wavy brown cross-lines on a lighter background is pretty much unique to this species, although the background colour can vary. Paler adults, such as the one pictured above, have been shown to result from more rapid development at higher temperatures - so have probably arrived from somewhere hot and dry like southern Spain. Globally, the species is restricted mainly to Europe although it has also been recorded in the Canary Islands.

The remainder of the 'big seven' are all 'micro-moths' - see another post for more about the differences between 'micro' and 'macro' moths. The first two lie within the Crambid family, which contains some of my favourite moth species.

At first sight, the Rusty-dot Pearl (below - from this morning) appears relatively undistinguished. However, once you have got your eye in, its characteristic warm orange-brown colour with (usually) darker oval and kidney markings coupled with a strongly triangular shape clearly point to this species. Globally, the species has a large range that extends from Europe to South Africa and Japan.

Rusty-dot Pearl Udea ferrugalis - Dorset 22.5.26

The second common Crambid migrant, Rush Veneer (below, also from this morning), is more variable in colour and pattern than Rusty-dot Pearl. Fortunately, its long and narrow shape cannot be confused with any other common British moth (although there is a similar American species). The one pictured below is quite light in colour: others can be darker. The species has a similarly wide global range to Rusty-dot Pearl.

Rush Veneer Nomophila noctuella - Dorset 22.5.26

The final 'big seven' migrant is anything but big! The Diamond-back Moth (below) is absolutely tiny, about 6-8mm in length. You can easily miss them in a moth trap. Yet this minute insect is one of the world's great travellers, turning up in every continent except Antarctica (although I bet that a few have turned up there as well that no-one has yet discovered). They fly both during the day and night.

Diamond-back Moth Plutella xylostella - Dorset 24.5.18

Identification is fairly straightforward (if you can spot them in the first place); in their characteristic form, the wavy-edged light patch on the back provides a clear contrast with the dark sides of the moth. Given their small size, some form of magnification is helpful to make this out.

Diamond-back Moths can arrive in huge influxes, and in some years are probably the most abundant of all of the 'big seven' migrants to Britain described above. For example, hundreds of thousands arrived in May 2000, probably from Southern or South-eastern Europe (Chapman et al., 2002). There were only five in my trap this morning, but to witness a mass arrival is an impressive sight that I have only experienced once - on the island of Inner Farne off the coast of Northumberland several years ago, where every bit of vegetation seemed to be dotted with tiny moths.

It's worth adding that Diamond-back Moths can be a serious agricultural pest. The Natural History Museum has published a short article about the species here.

Right - those are Britain's top seven most common migrant species. The next blog will look at those that are a bit rarer, but still turn up in sizeable numbers. Watch this space.

References

Chapman, J.W., Reynolds, D.R., Smith, A.D., Riley, J.R., Pedgley, D.E. and Woiwod, I.P. (2002). 'High‐altitude migration of the diamondback moth Plutella xylostella to the UK: a study using radar, aerial netting, and ground trapping.' Ecological Entomology, 27(6), pp.641-650. (link)

Chapman, J.W., Lim, K.S. and Reynolds, D.R. (2013). 'The significance of midsummer movements of Autographa gamma: Implications for a mechanistic understanding of orientation behavior in a migrant moth.' Current Zoology, 59(3), pp.360-370. (link)

Parsons, M. and Clancy, S. (2023) A Guide to the Pyralid and Crambid Moths of Britain and Ireland. Atropos Publishing.

Randle, Z. et al. (2019) Atlas of Britain and Ireland's Larger Moths. Pisces Publications.

See also the field guides and websites listed in a separate blog post.

Global range data is from GBIF.

Starting to Identify Moths (part 2) - What family?

 

I don't know about you, but my natural instinct when trying to identify something - be it moth, butterfly or bird - is to look at pictures in field guides or online. But with many groups of insect, this doesn't work. Differences between species, or even families, can be subtle or even invisible to a casual observer, making them difficult to illustrate by drawings or photographs. The normal identification method for many insects - from beetles to caddis flies - is therefore to use a key. This will set out a series of choices, allowing you (in an ideal world) to eventually reach an identification. Many insect keys require the use of lenses or microscopes, and in some cases dissection of genitalia.

Happily, moths (generally) are an exception. The good news is that most macro-moths and many micro-moths can be identified from obvious visual characters.  As a result, most moth field guides do not contain detailed keys. Instead, they rely in the first instance on the user matching their specimen to an appropriate image before consulting the more detailed identification advice in their species accounts. 

The bad news is that a beginner trying to identify a moth is faced with a bewildering variety of images, many of which - at first sight - look very similar to each other!

If you haven't already seen it then you may want to take a look at the first blog post of this series, which gives more detail about the identification resources that are out there (link: Identification Resources Blog Post). There are a lot and that list is growing. The purpose of the present post is to suggest a way of making sense of all of those pictures! 

(Disclaimer: I'm only looking at macro-moths in the context of Britain and Ireland. Once you leave these shores, it gets even more interesting - and even more complicated!)

(Second disclaimer: This post is not intended to be comprehensive; the idea is to describe the families and sub-families that a beginner is most likely to come across.)

A Route Towards Identification

Obviously, you can trawl through the many hundreds of drawings or photographs one by one, which is time consuming and can be dispiriting. A better way to do it is to narrow your search - and the easiest first step along that route is to work out which family your moth belongs to.

You will search in vain for a simple key to macro-moth families. Mainly, this is because their formal definition is often based upon obscure characters: these include genitalia, the pattern on veins on their wings and features such as ocelli (additional lenses sited near to the main compound eye) and tympanal organs (which sense pressure or vibration). In addition, some characters only relate to caterpillars (larvae), which is hardly helpful when you're looking at an adult.

The other complication is that families have a nasty habit of changing as more information becomes available to the taxonomists. Hopefully, things have now settled down, although I wouldn't bet on it.

[As an aside, if you are looking for a book about general moth biology and evolution I can recommend David Lees and Alberto Zilli's Moths: Their biology, diversity and evolution which is published by the Natural History Museum. Reasonably priced, and nicely illustrated, it includes images of moths from the British Isles and around the world (NHBS bookshop link here)]

Macro-moths and Micro-moths

The distinction between 'macros' and 'micros' is so well established that it comes as a bit of a shock to learn that it has almost no scientific basis whatsoever.  Apologies for a short detour into the world of taxonomy - the classification of life.

You can picture the evolution of moths and butterflies (which together make up the Order Lepidoptera) as a series of branches, as new forms have split off and diversified over millions of years. The older the split, the less that the modern day representatives of these branches are related to each other.

There are currently around 74 families of Lepidoptera (including the butterflies) on the British checklist (compiled by Agassiz, Heckford and Beaven in 2013, and regularly updated - link to the Natural History Museum data portal) . The checklist gives a two-part number to each species, the first part signifying its family, the second part being unique to that species. So the Vestal moth pictured at the start of this blog post has been given the number 70.038, meaning that it is the 38th species on the checklist in the Geometrid family (Geometridae) - family number 70. 

In simple terms, the families that are classed as micro-moths were the earliest to split off from the 'main' evolutionary line of moths and butterflies (around 100-200 million years ago). You could call them 'primitive', although their surviving members are actually as modern as any other living moth. Most of the macro-moths appeared on the scene later (around 80-100 million years ago). 

This evolutionary sequence is reflected in the checklist classification. Micro-moths, which comprise most of the moth families (around 50 out of 74), generally have the lower numbers, while macro-moths are generally higher.

However, to complicate things, a few of the more 'primitive' families are generally included with the macro-moths. The only reason for this is that they are large and easily observed. But they are only distantly related to the main group of macro-moths.

To bring this together, here is a list of the macro-moth families of Great Britain and Ireland, with their checklist number, scientific name, common name and the (approximate) number of resident species in our area - taken from the 3rd edition of Waring and Townsend (see my resources blog post for the detailed reference). This may look off-putting, but things are actually less complicated than they may first appear.

• 3. Hepialidae - Swift Moths (5 species)
• 50. Cossidae - Leopard and Goat Moths (3) 
• 51. Sesiidae - Clearwings (14)
• 53. Limacodidae - Festoon and Triangle (2)
• 54. Zygaenidae - Forester and Burnet Moths (10)
• 65. Drepanidae - Hook-tips and Lutestrings (6)
• 66. Lasiocampidae - Eggar and Lappet Moths (10)
• 67. Endromidae - Kentish Glory (1) - but don't look for it in Kent!
• 68. Saturnidae - Emperor Moth (1)
• 69. Sphingidae - Hawk-moths (9 plus immigrants) - everyone's favourites
• 70. Geometridae - Geometrids (around 300)
• 71. Notodontidae - Prominents, Kittens and Processionaries (21)
• 72. Erebidae - Tussocks, Tigers, Footmen and the like (89 species) - a mixed bag
• 73. Noctuidae - Noctuids (around 370)
• 74. Nolidae - (14) - another mixed bag that can easily get confused with some micros

Several things jump out of this list.

First, and most importantly, the vast majority of macro-moths are in two large families - the Geometrids and Noctuids. Getting a feel for these two is an important step in learning to identify moths. It's a pity that these families don't have better common names. Geometrids (or geometer moths) are named for their caterpillars, some of which loop along as if they are making a measurement ("inchworms"). Elsewhere in the world, Noctuids are known as owlet moths, armyworms or cutworms, but none of these names are used here.

Second, the Hepialidae (Swift Moths) are real outliers in an evolutionary sense - family number 3 on the checklist. Their closest living relations are tiny micro-moths, not that you would know it from looking at them - for example this female Ghost Moth (below).

Ghost Moth (female) - an 'honorary' macro-moth (one of the Swift moths)

Third, you will see that there is a 'gap' between the Zygaenidae (54) and Drepanidae (65). This contains two important micro-moth families - the Pyralidae (61) and Crambidae (62) - which both include a few species that are large, common and conspicuous enough to be confused with macro-moths. Mother of Pearl is a good (and common) example - see below. The butterflies are also found in this 'gap' - they are families 56 to 61 in the Checklist. I've done a separate blog post on the differences (or not) between moths and butterflies - link here.

Mother of Pearl - a big "micro" moth (family: Crambidae)

Going Forward - First, check out the Big Two

So, you have found a macro-moth. How can you can assign it to a family?

The first job is to check whether it is a member of either of the 'Big Two' families, the Geometrids or the Noctuids. Given that these account for over two-thirds of our macro-moth species, including most of our commonest moths, there's a good chance that it will be. 

(In Dorset, we publish an annual report that includes the Top Twenty most recorded moths for the year - downloadable free via this link. In 2022, all but three of these were in the 'Big Two' families.)

This post briefly runs through the moth families that you are most likely to encounter, giving typical examples from each one - starting with the 'Big Two'. The idea is that you should start to get a 'feel' for the characteristics of each family, which should help to narrow down your search for the correct species.

First, some typical Geometrids:

Typical Geometrid - Common White Wave

Grey Pug - another Geometrid (but pugs can be tricky!)

Mocha - a rarer, but lovely, Geometrid

Brimstone - an attractive and common Geometrid

Flame Carpet - the carpets are an important Geometrid group

Large Emerald - a stunning Geometrid

Early Thorn - a Geometrid that holds its wings vertically

While there's plenty of variety, it's also possible to observe a general theme. In Geometrids the wings rarely overlap and are usually held out flat like a basking butterfly. One group (the thorns) rest with their wings held vertically (or near-vertically); some other geometrids, like the carpets, will also sometimes close their wings above them. (This is annoying when you want to identify them.) 

Turning to the other 'Big Two' family, here are some typical Noctuids. Most will lie flat with wings partly or wholly overlapped (a good pointer) but a few adopt a more upright (tent-like) position, like the Silver Y pictured a bit further down.

Typical Noctuid - Clouded Drab (a common Spring moth)

Large Yellow Underwing - one of the commonest Noctuids

Flame Shoulder - another common Noctuid.

Hebrew Character - a common Spring Noctuid

Coronet (Noctuid) - can be a common where you find Ash trees.

Silver Y - a Noctuid with an upright (tent-like) stance. A common migrant species.

Again, there is a clear general theme - Noctuids are usually stocky or chunky moths, with wings either overlapping or lying side-by-side (but not spread out like a butterfly). Most wings sit fairly flat, but some rest in a tent-like pose. But do note that some other families contain moths with these characteristics, for example the Ermines, which are found in our next family ...

Not the Big Two? Check the next biggest family.

So, what about the other families? I'll deal with the next largest first (the Erebidae) and then move onto some of the smaller - and perhaps more distinctive - families.

For me, the Erebidae doesn't hang together as a family. Its members appear very diverse, with no obvious linking visual theme. And indeed the taxonomists have found them to be problematic; anyone with a first edition of Waring and Townsend (2003) will discover that this family didn't even exist then!

Luckily, however, they break down into a few distinctive groups. Here are some typical ones: examples of the Snouts, Ermines, Tigers, Footmen and Underwings (excluding Yellow Underwings!), which all live within this family.

Snout - common and frequently seen (Erebidae).

Buff Ermine - a common member of the Erebidae. Like many Ermines, this is easily confused with the Noctuids. 

Garden Tiger - my favourite of the Tigers (Erebidae) but sadly declining. Tigers are usually bright and colourful.

 

Dingy Footman - Footmen are a tricky group of the Erebidae

Red Underwing - sensational moths, but they don't like to hang around (Erebidae)

As I said, there is no obvious visual linking theme to this family, but each group (or sub-family) within the moths are generally distinctive.

Prominents - The Next Biggest Family

There may be only 21 species in the family, but some members of the Prominent & Kitten family (Notodontidae) will certainly turn up in your moth trap. Usually resting in a tent-like position like some of the Noctuids, they tend to appear more furry, and even more chunky, than most members of that family. Here are three typical examples:

Buff Tip - a crowd-pleasing twig-mimic (Notodontidae).

Pebble Prominent (Notodontidae).

Sallow Kitten (Notodontidae) - easily confused with Poplar Kitten.

Best of the Rest - Other Distinctive Families

Ignoring four families that are unlikely to turn up in your trap (but congratulations if they do!) - namely the Clearwings, Festoon/Triangle, Kentish Glory and Emperor Moth - that leaves us with seven more families that you are very likely to come across. Happily, most are pretty distinctive. Of these, three families can be easily identified: the Hawk-moths, the Eggars and the Burnet Moths. I'll start with these.

The Hawk-moths (family Sphingidae) are large and obvious. Even better, some are common. Here's two for starters:

Elephant Hawk-moth

Privet Hawk-moth - one of the biggest moths in Britain and Ireland

The Eggar moths (family Lasiocampidae) contain some of my favourite macro-moths. Like some other moths (for example most of the Notodontidae) the adults cannot feed. Most are large and particularly furry: here are two typical examples:

Oak Eggar (female)

Drinker - another Eggar moth

Although unlikely to appear in a light trap, the Burnet Moths (family Zygaenidae) are frequent and visible day-flyers in grassland and other open areas - especially sand dunes and flowery chalk grassland.  Look for them on flower-heads. This is the most widely spread species in Britain and Ireland:

Six-spot Burnet Moth

Four more families to go! I've already introduced the Swift Moths (family Hepialidae) with the image of a Ghost Moth earlier on in this blog post. These hold their wings in a tent-like position like some of the Noctuids, but have a fairly consistent, rounded wing shape. Very often the abdomen pokes out beyond the back of the forewings. Here's another characteristic Swift Moth species that may well turn up in your light trap:

Orange Swift - a common Swift Moth

Only three species from the Goat and Leopard Moths (family Cossidae) are found in Britain and Ireland. All have long wings, which are also held in a tent-like resting position. Leopard Moth is most likely to appear in a moth trap, although it is absent from Ireland, Scotland and parts of Wales and Northern England. A lovely moth with distinctive black spots on a white background.

 

Leopard Moth (Cossidae)

The Hook-tip and Lutestring family (Drepanidae) is another family that has caused problems for the taxonomists. It is divided into two groups (strictly, sub-families) that look quite different from each other. However, within itself, each group has a fairly distinctive character.

The first group (the Hook-tips) generally hold their wings out flat like the Geometrids. The clue to their identification is in the name - look out for the hooked tip to their forewings (although, as we'll see later, not all hook-tipped moths are in this family!). Pebble Hook-tip (below) is a common and typical example of the Hook-tips. 

Pebble Hook-tip (Drepanidae)

Having said that, there is one complete outlier in the Hook-tip sub-family - the Chinese Character. It is a common and fascinating little moth that mimics bird poo with great accuracy. It can be easy to miss.

Chinese Character - an unusual Hook-tip (Drepanidae)

The other sub-family of the Drepanidae are the Lutestrings. These look very like Noctuids, and I can't think of an easy way to separate them from that big family. However, there aren't very many of them and they are easily learned. First, a distinctive one; and then one that's a bit more confusing.

Peach Blossom - a distinctive member of the Drepanidae.

Common Lutestring - one of the Drepanidae that's easily confused with the Noctuids

And that leaves us with the Nolidae. Sitting after the Noctuids at the back of most field guides, these can get a bit overlooked. Like the Drepanidae, there is no obvious linking visual characteristic for the family as a whole, but also like that family, they are few in number and easily learned. Six of the family (all various kinds of Black Arches) do share a consistent 'look'. They are small, so there is a danger of confusing them with some micro-moths. Of these, Least Black Arches is the most widespread across Britain and Ireland, but it's still not common.

Least Black Arches (Nolidae) - not a micro-moth!

Very different, and rather more common (I'm happy to say) is the beautiful Green Silver-lines.

Green Silver-lines (Nolidae)

 Whew! Well done if you've made it this far.

Finally ... what's in a name?

There's been a lot to get through in this blog post, but I'll leave with a quick word of warning about common (or vernacular) moth names. The message in a nutshell is as follows: common moth names can be inconsistent and confusing! Many relate to visual features that can be found across more than one moth family. Do not assume that a similar common name implies any sort of actual relationship. 

For example:

• Black Arches (family Erebidae) is not related to Least Black Arches, Kent Black Arches and the others in the Nolidae family.

Black Arches (Erebidae) - no relation to the Nolidae.

• And the 'Arches' name applies to moths in other families as well - such as Green Arches (in the Noctuid family).

Green Arches - a Noctuid.

• Beautiful Hook-tip (also family Erebidae - which has a lot to answer for!) is not a member of the Hook-tip family (Drepanidae), although it really looks like one.

Beautiful Hook-tip (Erebidae) - not in the Hook-tip family (Drepanidae)

• There's a lot more of this, but I'll leave it there. There's more identification advice to come, so watch this space ...