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While butterflies are popular, iconic and colourful daytime insects familiar to everyone, moths have something of a PR problem. There seems a widespread misconception that moths are dull, boring and brown, and put on this planet to do little else than to chew our clothes and carpets. While a tiny minority do unfortunately have this tendency, and many can be brown, they are certainly not dull and boring as any moth trap will illustrate.

Moths

WHEN

Between May and July for most resident species of hawkmoth

WHERE

The moth trap can be placed anywhere from the garden to a local nature reserve

The angle shades looking less like a pair of sunglasses and more like a crumpled leaf.

Robert Thompson

The differences between moths and butterflies are numerous, complex, indistinct, and include frequent exceptions. The most obvious difference is that butterflies fly during the day, while the vast majority of moths are either crepuscular – flying at twilight – or nocturnal by nature. A close look at the antennae of the two groups will also reveal that most butterflies have slender antennae with a club on the end; moths either have feathery antennae or a pair of simple filamentous strands without clubs. In resting state, all of the butterflies, with the exception of the skippers, close their wings over their backs; moths, with the exception of the thorns, lay their wings alongside their bodies. Most moths also possess a frenulum, which is a small hook on their hindwings that attaches to barbs on the forewing, whereas the four wings of butterflies all operate independently. Finally, most moths tend to have hairy or furry-looking bodies, with larger scales on the wings to enable them to conserve heat at night, while the sun-loving butterflies do not need this extra insulation so have more slender thoraxes and abdomens.

Moths are also sub-divided into two groups called ‘macro-’ and ‘micro-’ moths based on their anatomical structure, but, as a few micro-moths are larger than macro-moths, this division can be complicated to the untrained eye. Virtually all macro-moths can be distinguished by the patterning on, and the shape of, the wing, which makes identification easier; the micros, on the other hand, invariably and unfortunately need their pressed genitalia to be examined down a microscope. Macro-moths are also much more numerous than our 59 resident butterflies, with over 800 species recorded in Britain. During a good night’s ‘moth-ing’ in the summer, the ‘moth-er’ can be rewarded with at least 100 species and possibly as many as 1,000 individuals from a specially designed moth trap.

That moths are attracted to artificial lights has been known ever since man made fire, hence the phrase ‘like a moth to the flame’, but the reasons why this happens are complex and still not fully understood. When watching how moths become attracted to a light or moth trap, it is very noticeable that many of the individuals appear to fly around the light in ever-decreasing circles, and the most common theory to explain this behaviour is that moths use a technique of celestial navigation called ‘transverse orientation’. By maintaining a constant angular trajectory to a bright celestial light such as the moon, the moths can fly in a straight line. As the moon is so far away the change in angle between the moth and the moon’s rays will be negligible, the moon will always be in the upper part of their visual field and no lower than the horizon.

‘Have the lambs stopped screaming, Clarice?’ The infamous death’s-head hawkmoth.

Stephen Dalton

Evolutionarily speaking, human light sources have been around for such a short space of time that the moths have not yet evolved the ability to ignore the light pollution we create. As a moth-trap light may be so much stronger than that of the moon when the insects are close by, they become confused and instead use the artificial light for navigation. But, as this light is below the horizon and the angle of the moth to the light changes markedly after only a short distance, the moths will instinctively attempt to correct this by constantly turning towards the light, causing them to spiral down to the light until they either hit it or drop into the moth trap.

A quick glance at any guide to British moths will soon make the reader aware of the infinitely varied colours of moths, with a number of species being easily as coloured and possibly even more intricately patterned than the butterflies. Many moths have been given wonderful common names as well, such as mother shipton, peach blossom or brindled beauty, which certainly adds to the fun of moth identification. Of all the wonderfully different 17 families of macros in Britain, though, without question the most spectacular group regularly encountered in moth traps are the hawkmoths.

The hawkmoths comprise about 850 known species worldwide and are most heavily represented in the tropics. The family includes such well-known species as: the infamous death’s-head hawkmoth that was immortalised in the film Silence of the Lambs; the day-flying hummingbird hawkmoth; as well as the long-tongued Darwin’s hawkmoth, which was predicted to exist by the great man after Darwin found an orchid that could only be pollinated by a proboscis of over 20 centimetres in length! The hawkmoths are moderate to large in size, with a wingspan of between 30 and 125 millimetres, and are characterised by their rapid flight, long, narrow hawklike wings and a streamlined abdomen, all clearly adaptations for quick and sustained flying. In addition to some species being able to hover, the hawkmoths are thought to be some of the world’s fastest flying insects, capable of travelling at 30 mph.

The larvae of hawkmoths are also larger than the vast majority of the other moth larvae, and can reach 80 to 120 millimetres long, with a surprisingly thick body and a horn clearly present on the eleventh segment, close to their rear end. The family’s Latin name, Sphingidae, comes from the posture adopted by the caterpillars: when they are resting on a twig, they cling to the plant with their pro-legs and hind claspers, while the front halves of their body rear up with the head curved back towards the twig, resulting in the caterpillars’ profile resembling that of an Egyptian sphinx.

The caterpillars have an incredible appetite and their weight before pupation may be ten thousand times that of when they initially hatched from their eggs; this means that, during their six-week larval stage, these ‘eating machines’ will have to moult at least three or four times. Although some hawkmoths are considerable pests to crops, such as the tobacco hornworm (hawkmoth) in the tobacco-growing areas of the USA, all of the British species confine their voracious appetites to a mostly abundant range of native plants.

The elephant hawkmoth derives its name from the grey, trunklike caterpillar, not from the startling pink and olive livery of the adult moth.

Laurie Campbell

If disturbed, the eyed hawkmoth will flash ‘the eyes’ on its hind-wings to give the impression that it is much bigger and scarier than it really is!

Robert Thompson

Some of the caterpillars, such as the poplar and eyed hawkmoths, are well camouflaged against their respective food-plants, with disruptive patterns making them difficult to pick out. However, a number of other species that feed on low-growing plants, like the immigrant spurge and bedstraw hawkmoths, often have conspicuous colours, presumably to act as a warning to birds of their distasteful nature, while elephant hawkmoth larvae have eyespots to startle would-be predators. Those caterpillars that avoid being predated will then bury themselves underground to pupate in the soil over winter.

In Britain there are nine breeding species, with a further eight that have migrated from continental Europe occasionally recorded at moth traps. The elephant hawkmoth is certainly one of those species that puts paid to the theory that all moths are brown, with its brazen pink and olive colouration. This small species is one of the most common hawkmoths in Britain and is widespread in England, Wales and southern Scotland. It is particularly common in urban areas, as its main food-plant is rosebay willowherb – that colourful coloniser of car parks, railway sidings and roadsides. The caterpillar is green or brown, speckled with grey, and has a pair of colourful eyespots on the fourth and fifth segments either side of the body, which become dilated when it is disturbed. The caterpillar’s body immediately behind the head is long and extendable and, when the caterpillar waves its head around while looking for the next meal, it has more than a passing resemblance to an elephant’s trunk, hence the name!

The hawkmoth most likely to be found as far north as Scotland, and even reaching the Arctic circle, is the poplar hawkmoth. The favoured habitats for this moth are any woodland margins, parks and gardens where the caterpillar’s food-plants of poplar, aspen or willow can be found. The adult has quite broad forewings that are coloured delicate shades of grey, have heavily scalloped trailing edges and a distinctive rusty-red patch at their base. When this quite large moth is at rest, it is very noticeable that the leading edges of both smaller hindwings poke out in front of the forewings – the frenulum is absent in this species – and the tip of the abdomen also commonly curls upwards.

Of course the holy grail of hawkmoth finds must be that of the death’s-head hawkmoth. The name of this most spectacular moth arises from the markings on its thorax, which bear a striking resemblance to that of a human skull and are complemented by the lateral stripes on the abdomen, which add a set of ribs to the image. This moth is the largest species regularly encountered in Britain and has been regarded in many countries as an omen of disaster, a myth possibly perpetuated by being the only known moth species to make an audible squeak when touched! The death’s-head is a native of Africa and migrates northwards into Europe each year, often reaching mostly southern Britain in small numbers by early autumn. The preferred food-plant of the caterpillar is the potato, but they will also help themselves to woody nightshade and jasmine. This is most certainly one species that any moth trapper would be delighted to hear going ‘bump in the night’!